Renew Magazine

With a badly damaged boot from the crash, I decided to make it a utility, with 160kg of batteries bolted to the back tray. The original gearbox and disc brake have been retained, close coupled to the electric motor, while the engine, exhaust, fuel tank and air cleaner have all been removed.

The front and rear bumpers were destroyed in the crash and have been replaced with aluminium bumpers. Standard 2cv tail lights have been recessed into the ute back and a Citroën logo has been glued in place.

The earth-covered library is a striking example of environmentally sustainable design. It was opened in September last year and cost $850,000—the money coming from the Federal Government’s Building the Education Revolution program. Why did Candlebark choose an earth-covered building? Architect Paul Haar says the school wanted to build in harmony with the sloping topography so as to keep the inspiring view of the valley below, and it needed a well-designed bushfire shelter.

Location and load-bearing materials
The library is on a south-east slope below Candlebark’s dining and meeting room, with a view into a valley of oak trees, elms and pasture. It sits on a concrete slab 4.5 metres below natural ground at its northern edge and meets natural ground level at its southern edge. The external retaining wall, made of 290mm core-reinforced concrete, is curved in a half circle. This shape more effectively resists the heavy horizontal forces placed by the earth on the wall. The south wall is curved to broader radius and consists mainly of tall counter-balanced double-hung windows and glazed doors that open to a terrace and the view beyond. Above the glazing, the south wall is framed in seasoned pine, sheathed both sides with structural grade seasoned pine plywood (to retain the edge of earth laid over the roof) and clad with fully compressed cement sheeting. Windows and external doors are framed in recycled Blackbutt hardwood and the pergola on the south terrace is made from salvaged exotic cypress pine.

About 500mm of soil covers the library roof. This depth of earth shields the building against radiant heat from sun and potential bushfire in summer, cold in winter, and stores enough moisture and nutrients to feed the grass and native ground cover plants that grow on the roof. To carry such a load of soil you would think the roof needed to be made of concrete or steel, but Paul says he stubbornly clung to the idea of an all-timber roof frame because of its sequestered carbon, easy workability and aesthetics. Massive post and beam portals of seasoned pine laminated veneer lumber (LVL) were made off site. LVL slabs were shaped and vertically screw laminated into roof beams that span continuously over posts of the same section. It took four men and a crane only 16 hours to erect the roof portals on site. Waste was minimised as off-cuts were used as purlins above the roof beams. Seasoned pine plywood was then laid over the roof purlins.

“In the end it turned out to be a really economical and attractive roof structure for an earth-covered building,” Paul says.

As an aside, the panels were placed landscape covering nearly the whole north/north-west roof. The purpose of this was two-fold, generating as much power as possible for the area and reducing the heat radiated from the roof into the ceiling cavity, with the panels acting like a safari roof. Since the panels have been installed the temperature difference between rooflines, when the sun is directly overhead is about 7°C, being  38°C for the roof under the panels and 43°C for the exposed roof.

Temperatures were measured in the ceiling cavity using an infrared thermometer, when the room temperature is below 26°C. Vents are still to be placed in the gable ends of the ceiling cavity to aid cross ventilation. So hopefully the house should be a bit cooler in the afternoons and evenings. So far this (mild) summer, we have not needed to use fans in what is usually an extremely hot room.

Uncertain output

Unfortunately I do not seem to be achieving the maximum benefit: output so far is averaging 20kWh per day. Output starts from as early as 5am and stops around 6pm. The problem is from around 9.30am to 3pm the output does not change significantly, staying in the mid 3000s.

Other systems I am familiar with have a definite peak as the sun moves overhead. One observation is that on overcast days, when there’s a sunny break in the cloud, output will jump between high 4000s to early 5000s for a few seconds, then down to as low as a few hundred before rising to mid 3000s. Returning to mid to high 2000s once the sun is again blocked by cloud cover.

Fortuitously my system has battery backup and is easily configured so that I will always get at least the current rate that the energy retailer charges for the electricity generated, irrespective of what they do with the feed-in tariff.

Further explanation

Without government rebates my costing for a nominal 2kW system is around $12,000. This is broken down into $6000 for panels (ten 200W panels), $2800 for an inverter/charger at Jaycar, $1500 for 10kWh capacity ex-Telstra gel battery pack, $400 for two 60 amp solar regulators and $1300 for installation. Such a system will generate 3285 kWh per year in the Sydney area. My nominal 3kW system produced 5091 kWh in the last 12 months so I have tried not to give over-optimistic figures.

The beauty of having a battery backup system is the flexibility of either selling the generated power to the grid or else storing it and using it yourself. This means that if you missed out on some of the generous feed-in tariffs offered in different states, you will at least be always guaranteed the current peak rate charged for electricity. From July 2011 it was 25c/ kWh or 35c/kWh if measured on a time of use meter, according to NSW figures.

Assuming that $12,000 was paid for the system (unlikely as the Federal Government Solar Credits Scheme would bring down the price) the return could be as much as 6.8% pa. This calculation uses the 25c rate: 3285kWh x 0.25c = $821.25.

A more serious investor would put in a system with double the number of solar panels and use a larger capacity inverter/charger such as one from Xantrex or Selectronics, resulting in an outlay of $22,000 and a return on investment of 7.5%. These returns, with their guarantees (the return will only increase over the next 10 years as electricity prices increase) make PV solar systems, particularly ones with battery backup, a very sound investment. Take into account the current Solar Credits Scheme then $3000 can be deducted from the capital outlay for the 2kW system lifting the return to 9.1% pa. The return on a 4kW system jumps to 10.3%.

Solar credits

Note that there is no tax on returns from these investments so, depending on your tax level, a normal investment return in the order of 15% could obtain the same monetary return. On the other hand, if you are a part-aged pensioner, as my wife and I are, and own your own house, then your part-aged pension could increase because the investment becomes part of the family home, which is a non-assessable asset. This will increase the effective return by a couple of percentage points, making a possible return on investment of over 10%.

We wash our clothes at night when the rate’s at 20c per kilowatt-hour, we don’t have a dryer so use the clothes line or, if it’s wet, the clothes horse in front of the fire. We turn everything off at the power point (including microwave) except the fridge and freezer. We don’t usually have the TV on until after 6pm, unless babysitting, but usually have the radio on.

We also power whatever we can using 12 volts from the stand-alone system. This includes 12 volt hand drills (converted cordless drills), fluoros over workbenches, charging cordless phones, charging cordless headphones, charging our Coleman camping lamp, running the CD/tuner, two 12 volt LED downlights and the media player and hard drive (they have voltage regulators built in and will operate from 11.8 to 14.5 volts). We also have a 12 volt to USB adaptor, with various leads to charge ipods and mobile phones.

I have also run a 12 volt feed from the batteries to our patio which powers our patio lights (I’ve removed the transformer) and a CD/tuner, which was a freebie from a mate. We also have a 12 volt pump for watering the garden.

My wife has finally sorted out all the paperwork with our supplier, after they buggered up the last couple of bills, so soon we will be able to see how much we are really saving.
Lee Saville

Panel orientation makes a difference!

I suspect a lot of people overestimate solar PV output for east and west facing panels. I recently recorded some figures when I stayed with friends near Coonabarabran in NSW (latitude 31°S).
On the property are two systems. Both have the same monocrystalline panels, with six panels in each system and no shading from buildings or trees. One system faces north with a 30° panel tilt and the other faces east with the same tilt. Both were connected to the grid in July 2011.

In 72 days, the north-facing panels produced 427kWh while the east-facing panels produced 310kWh, so the output from the east-facing panels was around 27% less.

I plan to compare the figures after they have been feeding into the grid for one year.
Ashley Campbell

Getting the units right

As a subscriber of a few years now, I’d like to congratulate you on the continuing excellence of the magazine. I look forward to its arrival every quarter.

As an engineer, I am continually irritated by people’s misuse of and misunderstanding of symbols and terminology related to energy—but not in your publication I hasten to add. I don’t think I have ever seen such misuse in ReNew except perhaps in readers’ letters.

Things like watts/hr instead of Watt-hours and the like are plentiful in the media, and especially so on the internet. Battery capacity is a particularly badly understood area. While it’s irritating, it is also understandable given that only people who followed the maths/science stream in high school are likely to have been formally taught such things. Unless you really understand the relationships between force, work, power and time it’s difficult to fully engage in discussions about energy.

My suggestion therefore is for an article or perhaps a series of articles explaining the basics of force, pressure, work and power in physical and electrical terms. I think there’s a real need for some basic knowledge to be disseminated. After all, knowledge is power (pun intended).

Anyhow, that’s my ten cents’ worth.
Neil Biggar

Thanks for the suggestion Neil, if other readers would like to see articles like this email us at renew@ata.org.au
Ed

High cost abatement PVs

I read with interest Alan Pears’ report on the concept of high cost abatement PVs (ReNew 116). I have to agree with everything he said.

What he did not cover was the fiscal side of the matter—money for greenPower is a finite resource so should be spent wisely.

Why should we as consumers pay 60c/kWh for domestic PV-generated electricity when we can get the same energy from (for example) large-scale wind for 9c/kWh? Put another way, we can pay a fixed amount per time frame (say $10 a week) and get 17kWh from PVs or 111kWh from wind. Which would you choose?

Productivity commission findings are that the abatement cost for domestic PV systems ranges from $400 to $1000 per tonne, which is very high on a global scale.

From a broad perspective, if as a society we put the same amount of dollars that have been put into domestic PV into large-scale wind, the green energy sent to the grid would have been seven-fold what we have, to say nothing of the night and winter time generation.

I am all for people having their own domestic PV systems, but why should the rest of us pay for this most expensive form of green energy?

Disclosure: I have grid-connected PV systems, for the generous feed-in tariff which all consumers are paying for.
Bruce Jeffery

Renewables better than underground cables

During the 2010 state election campaign in Victoria, the now-Baillieu government promised to implement all 67 Bushfire Royal Commission recommendations. The article in The Age on 12/09/11, Call for underground wires to cut fire risk, identifies issues being considered in relation to Recommendation 27. Instead of 20 tonne excavators digging through the bush and severely impacting fragile environments, a far better approach is to install alternate systems on properties, rather than incredibly expensive underground cabling. The cost of alternate systems could be borne by the government and the electrical transmission companies creating the rarest of outcomes: a win-win-win-win for the government, households, the electrical transmission companies and the environment.

Properties should be supplied with the appropriate systems, such as stand-alone photovoltaic (PV) systems, while others might need hybrid systems of PVs and wind, depending on the geographic location and the needs of each individual property. Residents should be fully supported to learn and manage these systems and not be lumped with a system they can’t manage. These systems should be maintained by an appropriate body for five years before becoming the responsibility of the property owner.

This approach is a far more sensible option, especially in rural/remote areas where the thousands of kilometres of underground cabling to only a few properties seems an outrageous undertaking.
Leon Trembath

We could not agree more. The ATA has been a contributing member of the Bushfire Powerline Safety Taskforce over the last 12 months, which has been considering bushfire mitigation approaches in fringe of electricity grid locations. The ATA has made the case that it will often be far cheaper for households to be provided with a stand-alone power system, under a properly managed service contract, than to pay for undergrounding or insulating of powerlines lines at hundreds of thousands or even millions of dollars per kilometre.
Damien Moyse
ATA Energy Policy Manager

Reducing fridge startup current

I recently converted a freezer to a fridge; the conversion was successful, with at least a 60% reduction in energy consumed, although I would expect this to be less during summer months. When I measured the starting current it was a whopping 180 amps from my 12 volt system and at times would drop the battery voltage too low for the inverter to cope. Upon measuring the phase angle between the starting and running currents, they were only displaced by about 15°. I expect this is standard for most small fridge compressor motors, as manufacturers do not consider correcting the phase angle as most of these units are plugged into a 10 amp grid powered outlet.

After doing a bit of research and reading I found that the best angle of displacement to provide maximum torque for the motor to start is 90°. I placed a 500 volt, 6uF capacitor bank in series with the starting winding. This required breaking into the three-pin starting relay attached to the motor, breaking the circuit and drilling a hole in the mechanism to bring out a wire to connect to the capacitor bank. The other end of the capacitor I was able to attach to an external terminal on the starting unit.

This modification reduced the starting current down to 60 amps and gave a far smoother startup in less time. At the moment of starting, my 600 watt inverter did not have any trouble starting the fridge, as the shorter starting time and lower current allowed the battery voltage to remain steady.

I believe this conversion will allow people with small to medium solar energy systems and inverters to be able to use standard off-the-shelf fridges. I would be happy to forward a schematic diagram to any ReNew readers who may need to reduce the starting current and increase the torque of any induction motor which has a start-run winding.

Out of interest, my system is a 720 watt capacity photovoltaic system with a 12 volt, 800Ah (C/10) battery bank and 600 watt continuous, 1200 watt surge capacity inverter.

Peter Rusanow, electenergy@yahoo.com.au

Peter’s modification is a good example of adapting off-the-shelf equipment to be a bit more efficient and much easier to run on smaller renewable energy systems. Unfortunately, most manufacturers don’t consider the use of their equipment on renewable energy systems when they design it, preferring to keep designs simple to keep costs down (which is fair enough, as most devices will never be used on small renewable energy systems).

We should state here though that this sort of modification can be dangerous if done incorrectly and that you absolutely must have a good understanding of electrical theory and practical applications before attempting any such modifications. These modifications will, of course, void any warranty on your fridge and should such modifications cause a fire, don’t expect your insurance company to pay up!

Lance Turner

Water loss was temporarily fixed by connecting a downpipe diverter to send rainwater to the pool. A 5000 litre water tank was installed so we could keep the garden alive despite water restrictions.

Other small retrofits, such as fixing the dilapidated ceiling insulation and adding reflective foil in the ceiling to deflect the summer sun, helped a little with thermal comfort and efficiency, as did dismantling one of the two hot water systems (the old electric one in favour of the newer gas model).

The tanks filled slowly as there was little rainfall. The pool stayed unused and the summers were still hot and the winters cold. Removing the old electric hot water system halved our electricity usage, but most of that was taken up by gas usage.

Our efforts had been ad-hoc; to really make a difference we needed to invest more wisely.

Thoroughly tested

Before launching into renovations we tested the house from high to low to find its thermal weak points.

We estimated the R-value of all the external surfaces of the house such as ceiling, walls, windows, floor, and the area of each, to work out how much energy, in kilowatt-hours, was flowing out of the house per degree of temperature per hour, day or year. We also estimated how much energy was captured from the sun through windows. We studied passive heating and cooling and were particularly interested in the Passivhaus standard from Europe and the concept of thermal comfort.

Our measurements, using the concept of ‘heating degree days’ and ‘cooling degree days’, showed that more energy was going into keeping the house warm in winter. A heating degree day measures how much heating (in kWh) is needed to maintain a desired temperature, in Melbourne say 20°C.

In reality, finding out how long a system takes to pay off is a complex equation. Location is one of the biggest variables, due to the differing levels of sunshine across this wide country. However, sunshine levels are probably more predictable than the other location-specific variable – the eight different feed-in tariffs across Australia’s states and territories. Darwin residents, for instance, enjoy the highest levels of sunshine in Australia, yet have no feed-in tariff to celebrate this rich resource. The ‘Sunshine State’ of Queensland, by comparison, currently has one of the highest feed-in tariffs available.

Then there is the question of the up front Federal Government incentive, the Solar Credits Scheme. Did you manage to access the five-times multiplier for your STCs (Small-scale Technology Certificates), or did you miss out and only receive an STC multiplier of three, thinking that it was only meant to drop to four in mid-2011 anyway?

In February this year the Alternative Technology Association’s Energy Policy Team crunched the numbers on just how long a standard 1.5kW grid-connect solar power system would take to pay off around the country. The study was carried out in the midst of a solar installation boom, spurred on by the Federal Government Solar Credits Scheme, where households were able to receive five times the amount of STCs that their system generates. At the time, many states had strong feed-in tariffs, with a number of these being gross, including NSW and the ACT, with 60c/kWh and 45.7c/kWh paid to solar households for all their electricity generated. With estimated payback times as low as four years in New South Wales at the time, it’s little wonder solar power systems were in demand.

Only six months later ATA’s Solar Payback Calculator has been revised showing a significant increase in the payback time of grid-connect solar power systems in most states.

What’s happened?

Since the beginning of 2011, feed-in tariffs in SA, WA, NSW and ACT have been reduced or scrapped, with at least one other state currently considering its feed-in tariff options. Last year these governments were applauded by clean energy advocates for their progressive solar feed-in tariffs. In turn, payback times in these states have increased by up to 15 years, while the reduction in the Federal Government’s Solar Credits STC multiplier from five to three means payback times in all states have increased.

In February a 1.5kW grid-connect solar power system installed in the ACT had an estimated payback time of five years based on a gross feed-in tariff of 45c/kWh and a STC multiplier of five. The scheme is now closed to new customers so the same system could take over 20 years to recoup.

Similarly, in NSW the payback time has increased from around three to four years under a 60c/kWh gross feed-in tariff before the mid-year STC multiplier drop, to in excess of 20 years today with the closure of the feed-in tariff.

Payback times are expected to increase to at least 11 years in SA with feed-in tariff changes in October. In WA, the net feed-in tariff of 47c/kWh reached its capacity and was closed to new applications. Electricity retailer Synergy will pay a 7c/kWh hour net feed-in tariff to WA customers under that state’s Renewable Energy Buyback Scheme, yet payback times for new customers will be around 20 years.

Where’s the potential?

Victoria, Alice Springs and Queensland currently offer feed-in tariffs to new customers in the 45c/kWh to 66c/kWh range, with payback times around seven to eight years on a 3kW system, based on only exporting half the electricity produced to the grid. Increase that grid export to 75% and a system in Queensland might pay back in six years.

The last six months show that feed-in tariffs can change overnight, so get in quick. In fact, ATA’s Solar Payback figures for Victoria include a second, lower feed-in tariff of 23c/kWh, which has been in place for many years now and will hopefully remain in place, despite potential changes to the premium tariff of 60c/kWh.

Price of PV

Ultimately one of the biggest factors in payback time will be the price paid for a system. While feed-in tariffs are disappearing, the retail price of a solar power system looks set to drop, says ATA Energy Policy Manager Damien Moyse.

“PV prices are one of the good news stories with regards to this technology. The history of solar PV prices over 30 years has seen a halving of system price with every doubling of global installed megawatts. The current word from China, where most panels are currently manufactured, is that global silicon prices are likely to drop again in 2012, meaning that off-the-shelf prices for solar PV systems should again reduce further next year.”

The STC factor

Household solar prices are also affected by the STC price paid as part of the Solar Credits Scheme. To make it easier for everyone selling and buying a small-scale renewable energy system, the Federal Government fixed the STC price at $40. Yet, the price the consumer receives is actually less than that, probably closer to mid to low $20s and unfortunately this is unlikely to increase.

“The large electricity retailers, who buy the certificates direct from solar PV installation companies, use their significant purchasing power to offer these companies faster purchasing, but at a much reduced price than the $40 stipulated by government. Given the unwillingness of the Federal Government to force electricity retailers to purchase only through the dedicated STC ‘Clearing House’, it is unlikely that consumers will see prices close to $40 per certificate any time soon,” says Damien.

Does it matter?

To make a system pay off earlier, as always, it comes down to how energy efficient your home is in the first place. “Reduce your electricity consumption first, then install a small PV system. Get your consumption down to less than 10kWh per day and then all you need is about a 1.5kW system,” says Damien.

Most people investing in household solar have already travelled the energy efficiency path and are switching to solar to help the environment, not for financial reasons. ATA member Stephen Whately says: “We don’t need to justify the payback times of our cars or holidays, why should you justify sustainable improvements to the home?”

In other words, don’t dwell too long on ATA’s latest solar payback modelling below, the figures are likely to change, and solar households are in it for the love, not the money.

Solar Payback Calculator

Assumptions

The calculations above are based on the following details.

Size and Price
• System size: 1.5kW and 3kW
• Installed cost, fully installed, before value for STCs is recouped: $4.50 per watt, or $6750 for a 1.5kW system
• System Retail Price to customer. This is calculated using the Capital City STC Zone. In SA for instance, a system is expected to produce 31 STCs over 15 years. Multiply this by the Solar Credits multiplier of three to get 93 STCs worth $2325. This makes the retail price in SA $4425 for these calculations.

Small-scale Technology Certificates (STCs)
• STC price for above modelling: $25
The fixed $40 price for STCs from small renewable energy systems is the price that liable parties (i.e. electricity retailers) are mandated to purchase these certificates for. The actual price received by the end PV consumer is currently significantly less than $40 due to off-market transactions established between certificate traders and liable parties that occur outside the SRES ‘Clearing House’, which provide greater liquidity to solar PV suppliers /installers but less value to the end consumer.
• STC multiplier: x 3 for first 1.5kW of system size (current from 1 July 2011).

PV Generation
• System degradation rate: 0.5% per annum
• 20% generation losses are accounted for within the PV system
• Panels are assumed to be unshaded, facing north and tilted at the latitude angle ± 5 degrees. Generation from panels not within this optimal range would need to be derated to account for lower generation
• PV generation has been defined using Peak Sun-Hours (PSH) as defined by the Bureau of Meteorology (1990-2008 averaged data, converted to tilted angle of panels, tilted to latitude angle). The final ranges within each are attributable to there being more than one PSH zone within that state, with the lower end of the range reflecting the PSH zone for the capital city and the higher end of the range being reflective of regional locations with reasonable population density. Annual generation for the two locations within each state are calculated using the formula:
Annual generation [MWh] = System Size [kW] x PSH x 365 x (100% – Generation Losses) / 1000
Where: Generation Losses was 20%.

The results for capital city and regional locations are presented as a payback period range in each scenario in the tables. As it turned out, for all states, the longer payback period in the range for each scenario represents the capital city for that state.

Feed-in Tariffs (FiTs)

FiT rate assumptions are outlined in the second column of the tables.

NSW: Given the NSW FiT was scrapped for new entrants in June 2011, ATA has modelled three scenarios for NSW; one involving the original rate (60c/kWh); one using the interim rate (26c/kWh); and one involving no FiT.

SA: Given the recent changes to the FiT scheme in the South Australian Parliament, ATA has modelled two scenarios for the SA FiT; the first involving the original rate of 44c/kWh (due to cease for new entrants on 1st October 2011); and the second involving the adjusted rate from the 1st October 2011 of approximately 22c/kWh (16c/kWh plus retailer ‘fair and reasonable’ contribution for the value of the electricity).

ACT: Given the cancellation of the ACT FiT in early 2011, ATA has modelled two scenarios; the first involving the original rate (i.e. 45c/kWh), and the second involving no FiT.

VIC: Given the uncertainty around the future of the Victorian Premium FiT, two scenarios have been modelled; the first involving a Premium FiT of 66c/kWh, with the second involving the traditional standard FiT of 23c/kWh (in case the Premium FiT is soon closed).

WA: Given the recent closure of the WA government FiT scheme, two scenarios have been modelled; the first involving the previous total rate of 47c/kWh, with the second involving only the ‘Synergy’ buyback rate of 7c/kWh.

Other Model Assumptions
Electricity export rate

For net feed-in tariff jurisdictions (NT, QLD, SA, Tasmania, Victoria and WA), ATA modelled two scenarios assuming a household exports 50% and 75% of the total electricity generated from their solar PV system into the grid.

For gross feed-in tariff jurisdictions (NSW and ACT), ATA modelled 100% export of the total electricity generation from their solar PV system into the grid.

Zones

The following Zones were used for the purpose of STC calculation:
• NT: Zone 1 to 2
• QLD: Zones 1 to 3
• SA: Zone 3
• Tasmania: Zone 4
• Victoria: Zone 3 to 4
• WA: Zone 2 to 3
• NSW: Zone 3
• ACT: Zone 3

Value of grid electricity

See electricity price column. The ATA’s calculations assume a 5% increase in retail electricity prices, yet it could be higher. If grid prices go up, you’ll pay back a system in a net feed-in tariff zone faster. This is irrelevant in gross feed-in tariff states, as you are not offsetting your household consumption with your PV generation in a gross metered situation.

• The inverter is replaced after 15 years at a cost of $900 per kW.
• Discount rate: 6%. This is an allowance for the reducing value of money over time.

Article by Jacinta Cleary. Solar Payback Calculator and assumptions by Damien Moyse and Dominic Eales of the ATA Energy Policy team.

This article appears in ReNew 117.

In 2010 the star rating scales for several appliances were toughened­—but there was no public information campaign about the good news that appliances had improved efficiency beyond the existing scales. And first home buyer schemes continue to ignore the potential to target them towards smaller, more energy-efficient homes and installation of on-site renewables.

As we move towards the transition to digital TV, millions of old TVs are being discarded, and valuable resources lost, because governments have largely failed to establish large-scale recycling schemes. Government has run frequent TV advertisements warning people to get ready, yet they make no mention of the importance of choosing an energy efficient set-top box or new TV.

Since TV energy labelling was introduced in late 2009, a new generation of very efficient 7- to 8-star TVs has appeared. Not only are these more efficient than older flat screen units, but they are also more efficient than traditional cathode ray tube (CRT) TVs. But the old, inefficient flat screen products are still on the market, so informed choice of high efficiency products is not guaranteed.

This demonstrates how fragmented government action misses opportunities to capture energy efficiency potential and leaves us with millions of energy wasting items of equipment. What a lost opportunity.

In my last column I described my bemusement at the mixed signals coming from governments about sustainable energy policy. I think it’s now clear: sustainable energy policy is a low priority for governments. At the national level, the twin forces of the political need to reach budget surplus by 2012-13, combined with the ideological agenda that a carbon price will fix everything, means support for sustainable energy is expendable. In some states, the combination of climate scepticism, environmental politics and efforts to make budget savings have led to cutbacks, and have fuelled public attacks, presumably to justify reduced assistance to sustainable energy. In NSW the government has even attempted to apply retrospective change to PV legislation—setting a dangerous precedent. Recent state and commonwealth budget statements have confirmed serious cutbacks. Things are looking bleak.

Are PVs high cost abatement?

Recently we have seen intensive attacks on subsidies for PVs as ‘middle class welfare’ and ‘high cost abatement’. There’s no doubt policymakers haven’t done well on PV policy. But it has worked both ways. The industry’s development has been hampered by ‘stop-start’ policy. Most states have chosen the more complex and less attractive net feed-in tariff over a gross feed-in tariff. On the other hand, many of the subsidies have been very generous.

But we need to put this into context. Governments have chosen to continue poorly targeted first home buyers grants that drive up house prices and reward those who build large inefficient homes as well as those who want modest sustainable homes. Industries such as car manufacturers and aluminium smelters have been treated generously. We also need to remember that the Howard government introduced, then doubled PV rebates as a blatant vote chasing strategy. Labor matched them as an election commitment. Similarly, states introduced feed-in tariffs to win votes.

More recently, the PV rebate cost was shifted from consolidated revenue to a charge on energy retailers—presumably to make it easier to meet the government’s deficit reduction target. Now governments have been caught as energy prices skyrocket, largely because of failure to drive energy efficiency and distributed generation by the flawed energy market structure.

So PV policy can hardly be described as well planned and consistent.

However, the positive outcome of this ad-hoc shambles has been a transformation of the PV industry. It is now geared to deliver large-scale roll-out, while prices have come down significantly. Part of this is due to the high Australian dollar, but sales and installation have been streamlined and we have ridden the dramatic economies of scale of accelerating global production.

Government now faces a dilemma. If it cuts the PV subsidies, demand may crash and it will be seen as anti-renewables. At the same time, it will be undermining adoption of a very popular emission abatement technology. But if it keeps subsidies, what level of support is needed to keep demand high enough to build this important industry? Good question.

According to my calculations, an unsubsidised 1.5kW PV system is now close to being a zero or negative cost abatement option for a household if it can be financed at mortgage interest rates and its output either replaces daytime electricity (on a time of use tariff) or is paid for exports at that rate. With predicted increases in electricity prices, the financial case looks good.

But this doesn’t mean finance at this interest rate will be available, or that people will act ‘rationally’ and install them without subsidies. This is no different from the behaviour of industry, who had to be forced by legislation to even look for very cost-effective energy efficiency savings that deliver rates of return of 20-50% per annum or better. We are not very rational about future savings.

One option would be to mandate PV installation, for example on larger new homes and new apartment buildings. People building large homes are clearly not struggling to get a modest roof over their heads, and over the long term, it is a good investment for them. For apartments, the split incentive problem due to the disconnect between developer and occupant is a serious market failure.

A bank that looks rationally at the economics of PV would see that its revenue will cover any additional repayments, so it actually enhances the home buyer’s capacity to repay the mortgage. And it provides insurance against future energy price increases. So government could encourage or require banks to offer ‘bonus’ finance to cover a PV system on any new mortgage.

Incentives or subsidies could also be focused on installations in areas where electricity networks are under pressure, where powerline losses are high and where solar radiation is highest. There is also a case for low-income households to be entitled to installation of PV, with repayments delivered via a charge on council rates: this would help insulate them from increasing energy prices.

There are lots of creative policy options to take PV away from being a political football. Let’s hope government has enough imagination to find a constructive path forward instead of undermining the future of the PV industry.

Nuclear backtracking

The recent Japanese nuclear crisis has set back the plans of the nuclear industry to expand. We have seen again how a single nuclear accident can force the evacuation of large areas of valuable land for many years, while causing massive short term economic and social dislocation. Surely nuclear generators should be required to carry insurance against such an event? Of course, if they did, nuclear energy would be much more expensive and would simply fade away. Interesting, then, to see the Japanese government providing assistance to the power company that owns Fukushima.

Alan Pears has worked in the energy efficiency field for over twenty years as an engineer and educator. He is Adjunct Professor at RMIT University and is co-director of environmental consultancy Sustainable Solutions.

Read the full article in ReNew 116

The farm came with a large home—16 rooms over five levels with two open-plan living and entertaining areas—the main selling point being we liked this style years ago.

The three concrete slabs stepping down the rolling red soil hills already had hydronic in-slab tubing, heated from a diesel furnace along with the tap water. Cooking was done by bottled gas, and there were three slow-combustion wood heaters in the two living areas.

Philosophy and design

We are very keen on sustainability and want to minimise our carbon footprint, both in the home and our farm’s beef production. We were prepared to spend some money converting the heating system for a large reduction in running costs and emissions. The farm has many large trees and limbs are always falling, so using solar-powered heating and hot water, boosted by a wood-fired heater, seemed like a sensible idea.

We found the solar collectors we wanted and set system parameters. Our plumber designed and built the conversion, changed the skylights, re-flashed the house and updated much of the water collection. We added ideas as it was built over several months.

The home

The climate is cool temperate with few frosts and the house is sited on a southern slope in foothills.

We are at latitude 38.005°. There is some unavoidable morning shading in winter from a roadside glider possum habitat of magnificent eucalypt trees over 40 meters high, 30 meters away and uphill on the northern road boundary. The outside temperature ranges between 2°C and 42°C but the house has such a large thermal time constant that living areas stay between 17°C and 22°C in winter, and no more than 25°C after a run of hot days.

The house design is classic 1970s double brick with rough-sawn, exposed beams in eight meter cathedral ceilings.It had hardwood french and other windows with single-glazing throughout, and sad plastic-vented skylights. Everything was coloured mission brown.

The designer ignored the 16 kilometre view to the Strzelecki Ranges and the valley below, and modern principles of house alignment for passive heating and cooling. However, at least the sun does not load up the interior. There are a few, small windows to the east, with excellent shading from canvas blinds, and large french windows to the west. These are shaded by a pergola and close battens. The home’s north face is stepped into the hill and the windows are totally shaded by a brick cloister with archways: a very sensible design providing a great spring breakfast area.

The kitchen, living and lounge rooms, study and billiards rooms are open plan and interconnected on three levels, which does create air currents, especially with such high ceilings. We have been slowly renovating, as one does with a retirement income.

The aim is to convert major glass in living areas to high-efficiency glass and to install as much double glazing as we can afford. So far our plumber has retrofitted seven double-glazed, openable skylights. The local glazier replaced 11 clearstory windows and made three panels openable to draw up cooling air from the lower levels when a summer cool change arrives.

We use pressurised tank water for most of the home, buildings and farm animals. There are 245,000 litres available in concrete tanks, linked by a 50mm buried ring main. Our local irrigation contractor built a fire sprinkler system for all buildings on the farm, which was essential when the wind changed during the Black Saturday bushfires in 2009. Our 100-year average rainfall is 1100mm; we received 1178mm in 2010 so we always have an excess of stored water.

There is a 1.5kW solar power system on the roof, bringing an income and well offsetting the minor energy drain from the small pumps moving water into the hydronic heating and up to the solar collectors.

Hydronic system components

Our heating system has three sources of heat:

• 36 solar-collecting vacuum tubes (rated at 5.8kW)
• wood-fired, slow combustion fire, with flue water jacket
• two gas-fired instantaneous hot water boilers.

The service courtyard where most of this hybrid heating and hot water system is hidden looks Heath Robinson, but it is a credit to our local green-accredited plumber at Baw Baw Plumbing and his team. He always knows about the latest efficiency innovations and was a terrific speaker at our Landcare group’s Green Energy field day.

Heat storage

A custom made 1000 litre stainless steel tank with 75mm of insulation and a small header tank is the heat storage. It’s similar to those made for the local dairy industry. Hot water is not drawn from this water but via three heat exchanger coils in the tank, with the solar one at the base, the hydronics one at the centre and the hot water service at the top. Each is 11 metres long.

Solar collectors

I contacted eight retailers advertising evacuated tubes. Disappointingly, not many responded.

From sellers’ claims, the most efficient collectors I could find were Ritter (labelled APR), a Chinese-made German design imported by Sunplus CPC. We bought 1.6m long evacuated tubes in banks of six, with parabolic mirrors to direct extra sunlight under the tubes. Our budget limited us to triple the normal number of tubes recommended for hot tap water and a 1000 litre hot water storage tank.

The collector bank of 36 tubes is fixed to a 1.6m by 4.4m aluminium frame facing 15° west of north. I asked for it to be tilted steeper than the roof’s 17° at a calculated winter solstice angle of 60° to collect maximum energy for winter. This reduces excess summer yield and steam problems.

Importantly, the plumbing route for the tubes allows us to add more down the track.

The north roof with evacuated tube collectors for the heating system and a 1.5kW solar power system.

Inside the solar control and storage area

Solar-heated water pumping

This is a rainwater-filled closed loop heat-exchanger. Water from the storage tank coil is lifted about five metres up to the solar array by a 3-speed 30 watt 240v hot water pump with throttling valve, giving infinitely variable flow. It usually runs at 0.2 bar boost. A Zilmet model 20013 50 litre cylinder stores system over-pressure up to four bar from summer days, backed up by a blow-off valve to save water loss on hot days.

Relief valves

Four high spots in the solar array and wood heater circuits have auto air-bleed valves, allowing only air and steam to escape.

Wood-fired slow combustion heater

We changed the third wood heater to a gas unit for quick response to a cold home.

After the first winter with the new system, an existing free-standing Saxon unit in the living room was retrofitted with a 550mm tall stainless steel heat exchanger in the first part of the flue. It burns quietly from late autumn to early spring on wind-fallen mountain ash and blackwood harvested around the farm. Water to the flue exchanger is drawn from the base of the storage tank and delivered back to the top. Piping is about 25 metres long and rises about 3 metres. It is insulated with 25mm thick foam tubing and cased in colorbond. A 240v thermostat in the output pipe in a wall behind the heater senses output temperature and controls another small circulating pump at the storage tank, moving two litre slugs of hot water at 50 °C into the storage tank every few minutes. This heater provides around half our total hydronic heating in winter.

Gas boilers

Tap water is delivered via an instantaneous Rinnai V1500 gas boiler which adds heat if stored water is not 50°C. There are no adjustments for the home owner. Electronics in this unit can be damaged by our emergency home generator, so we cannot run the hot water when mains power fails, which it does for several hours at least four times per year.

Hydronic water supply is delivered to the mixing valve via a Sime Format 34e instantaneous gas boiler, rated at 11.2kW to 34kW, large enough to heat the whole home on its own. It adds heat if needed and has user-adjustments for output temp (set to 35°C). Its instruments display output temperature and pressure. The pump within this unit is also triggered by the thermostat in the master bathroom, sending heated water to a Hydrotherm P-600 Platinum tower rail, 2.2m by 600mm wide, helping provide some extra hydronic heating to the bathroom.

Both boilers stay on in summer as they do not use any gas unless heating water.

Heat users

The house is heated by hydronic coils in five zones in three concrete slabs at descending levels in the house, plus a fan-assisted radiator in the living room. Two manifolds are fed from a mixing valve, and water circulated by five, 240v Grunfos thermostatically-controlled 3-speed pumps.

We have only activated the outer coil on the lower slab coils. We are very fortunate that it flows via the master toilet and bathroom, laundry, kitchen, two guest bedrooms and to the living room on the lowest slab.
Hot tap water runs throughout the house with all piping insulated with 25mm thick foam tubing. External piping is further encased in 90mm stormwater piping.

Water delivery controls

Hydronic water is blended by the original tempering valve supplying two hydronic manifolds. Tap water is held to 50°C by a Reliance Heatguard Ultra tempering valve. This setting can be altered.

The three room thermostats in the home are very clever Honeywell model CM 907. They can be programmed in time blocks for every day of the week, can be over-ridden for one time block, set to a fixed temperature and adjusted for daylight savings. The lower slab thermostat in the living area also masters the upper slab in the entertainment area. The second thermostat in the upper level study controls the mid slab. The third thermostat in the master bathroom controls water to the towel rail.

Operation
Solar control

The electronic differential controller, made by Whitnic Services of NSW, gets its data from 10volt thermistors, one at the array output and one at the storage tank top. It has three modes and a red light indicates the pump is on, which I positioned to see from the back door.

Gas supply

Gas was originally supplied by a bank of 40kg cylinders. These were replaced by a 190kg truck-filled tank, with pressure reducers at two boilers, and a circuit supplying the guest kitchen and fast-response gas heater in the living room.

Owner adjustments and monitoring

I wanted to monitor input and tank temperatures, so I bought three $10 electronic indoor/outdoor thermometers with remote sensors and mounted them next to the differential controller. I can feel the input arriving from the solar array, with one attached to the lowest hot connection on the storage tank, indicating roughly how much hot water is in the tank, and the other reads water delivery to the taps. These have max/min displays as well, useful for checking array performance or pump adjustments. An old clock-type dial indicator measures the temperature of water returning from the hydronic system, a rough indication of how much heat is in the slabs.
The electronic gauges are particularly useful to know how much heated water is available for a big load such as a spa fill or running the lounge room radiator. Monitoring incoming temperatures from the array allows me to tune up the flow rate for best performance just below steam occurring, and tells me if we have any problems when it’s pumping. An improvement would be digital readings from the differential controller’s thermistors.
We can adjust slab heating times in two zones and towel rail temperature, and boost heat in the lounge room by activating the fan-assisted radiator. We can control the temperature of the water leaving the fire water jacket. We cannot alter the temperature trigger points for the solar array. It might be useful to keep it pumping above 80°C to stop a steam blockage occurring.

Current settings

Thermostats have six available time block settings, with the initial settings for the slab thermostats listed below:
TIME      TARGET TEMP
6am          20°C
8                18°C
Midday   18°C
5.30pm   18°C
8.40pm   13°C
10.30pm 8°C

When there’s a run of low solar-energy days we run the wood fire hotter. When there’s sunny days predicted, we can use less wood, or not light it.

As autumn starts, we open the hydronic valves and drive the wood heater hard to put as much heat as possible into selected slabs prior to cold snaps and overcast winter days. On a run of overcast days we open the damper on the wood heater.

Fine tuning and problems

We run the collector pump at the lowest of three speeds and fine-tuned the flow to 1.5l/min on the advice of the plumber. We’ve learnt that in summer we need to double the flow rate to avoid excessive pressure build-up.
The original thermistor on the solar array burnt out after one year and the surrounding insulation was charred! The new importer tells me the replacement thermistor is a tougher type.

Anything that stops the circulating pump while there’s sun on the vacuum tubes can create a blockage in the circuit that the circulating pump cannot overcome. When the thermistor on the roof fried, and when we lose power when the sun’s on the tubes, pressure builds up and the closed loop finally drops below it’s 0.2 bar pre-set pressure. This stops circulation for that day and we lose a little water as steam. When the pump is alive again it fails to get water circulating if the array is in sun. So if the system pressure gauge is zero, I know circulation has stopped and must be topped up. To fix it we fit the garden hose onto the fill point just below the pump, and run cold water until there are no bubbles passing the sight gauge. Our plumber has suggested an automatic supply for this.

Maintenance

Particle filters in the inlets to the tap boiler and both tempering/mixing valves need to be cleaned annually, the latter by removing the fitting gland, which is not a good design.

The Zilmet pressure storage tank needs its quiescent air pressure checked annually, and the whole tank replaced every five years. Pressure cylinders on my Citroen last indefinitely, with re-gassing, so we’ll see. The system needs to be de-pressured for accurate pressure checks.

The solar collector array needs to be hosed periodically to remove leaves.

Costs

Our gas costs about $730 for 550 litres per year, but my urban mate pays a fraction of our price! We really only use significant gas when we have guests, then it goes through the litres when the large boiler is doing a lot of the home heating. We average about 66 mjoules of gas per day in winter, and as little as 19 at other times. The Elgas truck doesn’t come from October to late April. In 2010 we used half the gas of 2009, mainly due to better windows and remembering to keep bedroom doors closed. We will get further significant reductions when our window conversions and internal glass partition are finished.

Total changeover cost, including towel rail and some bathroom alterations, was about $11,500 against an estimated $17,000. The local shire gave us a rebate of $250 and we received another $6900 in rebates. If hydronic slab heating was built into a new home, it may not be any more than other hot water and heating systems. Our 44 RECs were not sold because the supplier did not have an approved system with the tank size we used, so we missed out on around $1500. That’s a little plus for the environment as energy companies had to find an extra 44 RECs somewhere else.

Changed family habits

The dog is often asleep on the hottest sections of the hydronic loop, always in doorways or on the top of stairs. The cats love the laundry benches in winter.

To minimise the generation of greenhouse gas and gas bills we use most of our hot water first thing in the morning, giving the solar array the first opportunity to recover hot water lost. We built a wooden, pull-down rack below the laundry ceiling which now dries much of our cold weather washing.

We need to shut off the hydronic valve when spring is well-entrenched and must remember to open it when the first cool weather is predicted after Easter.

What next?

We are part-way through replacing most open-plan area windows with double glazing, with low U and SHGC value glass and argon gas in the space.

At the moment glaziers are installing a glass, openable air barrier at the top of the living area. This will zone the home into separate living and entertaining zones, reducing wood demands and cold air currents up the kitchen.
Stopping heat escaping is next. After a government-funded home assessment, this air entrapment work was to be financed by the now defunct Green Loans scheme. Another task is resealing all doors, and chasing air leaks along the brick-ceiling interfaces throughout the living spaces and external walls. This is to stop bushfire embers and smoke ingress; the home is to be a refuge as we’ve spent a lot of money on a 10-hour fire sprinkler system for all buildings.

I’m also planning to have the roof re-pointed; it’s amazing how much heat escapes from the fabric of the cathedral ceiling when you remove a capping tile on a cold day.

Much of the living room slab could be heated, in cooler weather, by direct sunlight, and possible when we replace dark green fibreglass on the pergola outside with clear sheets and retractable shade cloth.

I’d like an automatic system to over-ride the pump control in the main gas boiler, so the rail can be heated when the slab hydronics are off. This will probably involve some extra 240v relays to override the pump’s under-temperature and gas supply controls, which stop the pump when the hydronics are not on.

Due to firebox corrosion we will soon replace the wood heater. The next one will have a wet-back for more hydronic capability.

Suppliers

Green-accredited plumbers—Baw Baw Plumbing, Buln Buln East

Solar equipment suppliers—Phazer, Warragul

Glaziers—Walkies’s windows and glazing, and Warragul glass and glazing

Flue heat exchanger, gas room heater—Cosy heaters, Warragul

Monitoring thermometers—Dahlsens, Warragul

Fire protection system—The Farm Depot, Warragul

Gas heater installation—West Gippsland gas services, Warragul

Measure power use for a day

I measured the current drawn by each piece of 12 volt equipment (all the appliances and van fixtures that would be used while we are camping away from 240 volt power). This can be measured with either a clip-on ammeter or by inserting an ammeter temporarily into the circuit (most cheap multimeters have a 10 amp DC range). Or you can simply calculate the current by using the wattage marked on the 12 volt appliance or light globe i.e. current = power in watts divided by 12 volts, e.g. the current drawn by a 24 watt light globe connected to a 12 volt battery is 2 amps.

I estimated how long (in hours) each of these appliances will be used each day and entered it in a table. Minutes can be converted into fractions of an hour by dividing them by 60,  e.g. 10 minutes = 10/60 = 0.17 hours. To calculate the amp-hour (Ah) usage for each item listed, multiply the current drawn by each appliance by the hours (or fractions of an hour) you expect to use the appliance each day. Finally, add up the ‘Approx Amp-hours usage each Day’ column to give the estimated total daily amp-hour usage figure for each day.

In the sample table (p 25), the ‘Total daily Ah usage’ came to 29Ah per day, which is rounded up to 30Ah per day. The total power required for a 14 day stay would be 30Ah x 14 days = 420Ah. In a domestic caravan it would be impractical to try and carry enough batteries to last that long because of the weight and the cost.

Finding power when bush camping

The best option was to solar power my caravan. There are some down sides to solar; most caravan systems aren’t large enough to run a microwave oven or air conditioner, so you must ask yourself ‘Can I live without those items?’ You also need a back-up system very occasionally for long stretches of cloudy or rainy days.

Knowing that we needed 30Ah per day I selected a 12 volt, 80 watt solar panel, which will supply us with around 30Ah per day (i.e. approx 5 amps x 6 hours = 30Ah) and a bit more on good sunny days. To harvest this much power from an 80 watt solar panel I found that I needed to track the sun rather than just sit the panel in one position and have the sun pass over it daily. I manually move the panel three to four times per day to maximise the power output from the panel. (For an automatic solution, check out www.campatracka.com—Ed.)

If your choice is to use a fixed panel then you may need to buy a higher wattage solar panel than I used or otherwise reduce your daily power usage. My BP 80 watt panel cost approximately $800 a few years ago, although prices have possibly come down now. Discuss what will best suit your application with the solar panel supplier.

Cloudy and no sun?

I chose a 130Ah battery. It weighs 30 kilograms, which is light enough to carry around and lasts me 4.3 days using 30Ah per day before the battery  fully discharges—normally enough time for the sun to return. I typically only rely on my battery for two days and then I reduce our daily power consumption because discharging batteries below 50% of their capacity shortens their life. To cut back on power usage we don’t use anything powered by the inverter (unless essential), don’t read so long in bed and don’t use the laptop or television as much. By following these simple steps we can easily halve our daily usage.

If it’s still cloudy after three days then I charge the caravan battery from my tow vehicle. I have installed a 12 volt MotorMate charger in my caravan next to the battery and it delivers 13.8 volts at 20 amps directly into the van battery. By running my tow vehicle motor for 30 minutes I can put another 10Ah back into the van battery, giving us enough power to last almost another day on our reduced power rations. In nearly 200 nights that we have bush camped with this set-up, I’ve only had to use this method of charging four times.

This 12 volt charging system does require quite heavy cabling and Anderson plugs between the vehicle alternator and the van charger. This is because currents of over 30amps can be required, although voltage drops aren’t very important as the charger will work with input voltages as low as 8 volts. I spent a lot of time researching this subject because I wanted to know it would work before  spending $240 on a charger.