Towards grid independence

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What happens when a home with very low electricity use adds a battery? Terry Teoh describes his home’s interesting results.

OUR house is an Edwardian three-bedroom brick home renovated in 2010 along sustainable design lines. With two occupants, our house achieves a very low average electricity consumption of 2.4 kWh/day, though note that gas is (currently) used for space heating, cooking and boosting of solar hot water.

We installed a 5 kW solar PV system in December 2016. With the array oriented east and west, the seasonal difference in energy production is accentuated compared to a north-facing array: our system produces on average 26 kWh/day in summer and 7 kWh/day in winter.

In April 2017, we added a 4 kWh Sonnen eco8 battery to our system to provide solar load shifting—storing solar energy produced during the day for use at night.

In the first two months of operation (to June 2017), our house has moved from 30% to 70% grid independence—i.e. 70% of our energy is now generated by our solar system.

Interestingly, that 70% is lower than we expected given a substantially oversized solar array and battery. It turns out that our standby energy usage is too low to be served by our inverter!

However, it’s still a good result and the battery has lifted solar self-consumption from 5% to 50% and paved the way for us to disconnect from the gas network and move to an all-electric, renewably powered household.

Motivations
Our motivations for installing a battery system included a desire to maximise solar self-consumption and grid independence. The latter is not out of antipathy for energy companies or the grid. We want to stay connected to the grid.

The grid is good; it will just be used in a different way in the future to support a decentralised energy system where consumers will have more control over how they make, use, store and share energy.

Read the full article in ReNew 141.

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