Return in Light
In 2016, eco-housing development The Paddock asked for Renew’s help in designing its energy management approach. It was the first opportunity we’d had to test our Sunulator model—and the philosophy that informed its design—in a real-world setting.
The proof was always going to be in the pudding. Now, four years later, the first results are in… and as Damien Moyse explains, we’re delighted to find that the pudding tastes very good indeed!
Readers of Renew may be familiar with an eco-housing development that we have showcased a few times over recent years: The Paddock, a 1.4 ha site in the central Victorian goldfields town of Castlemaine.
Back in 2016, when the project was in its early stages, the developers asked the energy team at Renew (or, as we were then, the ATA) to advise on the best energy management approaches for the 27-home development. We were delighted to take the opportunity to test our ideas in a real-world situation, and agreed to take up the challenge.
The first seven homes were completed late last year, which means they have been occupied for nearly 12 months. The developers recently supplied Renew with electricity bills and smart meter data from November 2019 onwards (approximately eight months including summer, autumn and the start of winter). In other words, we were presented with data that would allow us to see how successful our energy management strategies had been.
So here’s the good news: those strategies have proven very successful indeed! In fact, the houses have performed better than we predicted: they are consuming between 25% and 40% less electricity than predicted, and use around 80% less input energy than typical, new Victorian homes built in 2020.
This is obviously an extremely gratifying result, and we’re delighted to share it with the world. It also gives other prospective homebuilders a deep insight into how to construct an energy efficient home—so in this article, we’ll do a deep dive into the data, and explain what it reveals.
Taking up the challenge
From the outset of the project, The Paddock’s developers (Heather and Neil Barrett) and the project architect (Geoff Crosby) have been committed to working within the framework of the Living Building Challenge (LBC) through planning, design and development. The LBC is a rigorous global standard with a holistic approach to sustainability, and “calls for the creation of building projects at all scales that operate as cleanly, beautifully and efficiently as nature’s architecture.” To be certified under the Challenge, projects “must meet a series of ambitious performance requirements over a minimum of 12 months of continuous occupancy.”
This was the first opportunity that we had been given to test our emerging philosophy on all-electric homes on a real-world project. The key components of that philosophy were:
• High thermal performance of the building shell (in the 7.5 to 8.5 Star range);
• All-electric appliances (no gas or wood);
• Ensuring high efficiency for major appliances such as hot water and heating/cooling systems; and
• On-site generation of renewable electricity.
Renew’s all-electric philosophy also had to be combined with the specific energy requirements of the LBC. These dictated that 105% of the project’s energy needs had to be supplied by on-site renewable energy on a net annual basis, without the use of on-site combustion (i.e. no gas or wood).
In addition to this, projects also had to provide on-site energy storage for resiliency, demonstrating that enough backup battery power was installed to cover:
• Emergency lighting (at least 10% of lighting load); and
• Refrigeration use for up to one week.
In order to demonstrate that the project could meet these requirements, Renew needed to:
• Construct a plausible load profile for each dwelling—considering all appliance energy use and differing dwelling sizes—on an annual basis, while taking into account daily and seasonal variability (e.g. peak winter heating and hot water);
• Simulate solar generation for different system sizes against those household load profiles, in order to understand the minimum solar system sizes required to achieve the 105% benchmark; and
• Construct separate lighting and refrigeration loads in order to understand the required level of storage for each dwelling.
Using an early version of the Sunulator—our solar simulation model—Renew built an annual electrical load profile broken down into 30-minute intervals. This profile divided the dwellings into four types, based on their size, and modelled energy usage for each.
As is well known, most residential loads are composed mainly of the power used by space heating/cooling and hot water appliances (in the order of 50% to 75% in total for most homes). In the case of The Paddock, given the site’s central Victorian location, heating and hot water were the two most important considerations. As such, we chose to analyse the most efficient heat pump air conditioners and heat pump hot water systems.
At the time of Renew’s work, the project architect already had preliminary designs for the dwellings, with an intention to achieve building energy ratings of around 8.5 Stars. As such, Renew used the megajoule per square metre (MJ/m2) benchmark from the Nationwide House Energy Rating Scheme (NatHERS) for the closest climate zone (Ballarat). Ultimately the final building designs would average 8.2 Stars.
Solar generation analysis
Our Sunulator was also used to simulate the solar generation for each dwelling, to ensure compliance with the LBC requirement.
The key factor in Sunulator’s accuracy is the integration of location-specific solar insolation data within the model. The closest location for which Renew had BoM data was Bendigo (less than 40 km away from the site).
Renew modeled three PV system sizes (3 kW, 4 kW and 6 kW) as part of the solar-only simulations. The results are set out in Table 2. As per the load analysis in Table 1, the 105% requirement for the various dwelling types (A, B, C and D) were 4768, 5039, 5470 and 5703 kWh, respectively.
As such, the key takeaways from the modeling were that:
• The 3 kW system is too small to meet the LBC requirement for all dwellings;
• The 4 kW system easily meets the requirements for Dwellings A, B and C, and also narrowly meets the requirement for Dwelling D.
Given the variability of actual loads that would eventuate once the site was developed, Renew recommended a minimum 4 kW of solar PV per dwelling. The developers followed this recommendation.
The LBC requirement for storage included a requirement that the project demonstrate sufficient backup battery power to cover:
• Emergency lighting (at least 10% of lighting load); and
• Refrigeration use for up to one week.
To inform the design of the storage system, Renew modelled a level of refrigeration and indoor lighting loads for one week, along with an additional 10 kWh per day for outdoor and common area lighting across the site. The results gave the weekly storage capacity requirements across the site, and per dwelling, set out in Table 3.
The required 9 kWh of individual storage per dwelling is significant (and in 2016, was very costly) in the context of what will be ultimately a grid-connected site.
The site was developed as an embedded network (or micro-grid), with one point of connection to the local distribution network—a consequence of the fact that the site was community-titled. However, the electrical engineering costs to develop the micro-grid to accommodate more cost effective centralised energy storage (as opposed to separate, per-dwelling batteries) were too high. (Some were three times the price). Mandating batteries for all residents was decided to be imposing too high a cost.
As such, Renew recommended monitoring developments in the market regarding storage and micro-grids. In the future, Renew believes there is likely to be a strong economic case for maximising the value of shared solar and storage across all tenants within small to medium sized eco-developments.
Actual dwelling performance
The first seven homes have been occupied since late 2019. Renew was supplied with electricity bills and smart meter data from November 2019 onwards (approximately eight months including summer, autumn and the start of winter).
So how have the houses performed? The data is set out in Table 4, and as we can say, they’ve performed very well indeed:
• The seven homes have a total average daily consumption of 7.6 kWh per day, for the eight-month period;
• Adjusted to include two higher winter months (July and August), Renew estimates their total average daily consumption would be approximately 9.0 kWh per day, for a full 12-month period;
• This compares to Renew’s 2016 prediction of between 12 and 15 kWh per day—meaning The Paddock homes are consuming between 25% and 40% less electricity than predicted!
The performance of The Paddock’s dwellings can be compared to typical, new homes built in Victoria. Typically, these:
• Are no better than 6 Star energy rating (and sometimes worse);
• Are “dual fuel” (i.e. have mains gas and mains electricity connected);
• Use gas for heating, hot water and cooking; and
• Consume approximately 12 kWh per day of electricity and another 100 MJ per day of mains gas.
By comparison, The Paddock dwellings use around 80% less input energy than typical, new Victorian homes built in 2020. This is an amazing result and one that both vindicated Renew’s original advice and actually exceeded expectations!
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