Better appliances to work with rooftop solar PV systems

Households and businesses with rooftop solar PV systems produce so much electricity in the middle of the day that feed-in tariffs are going down fast, and there are moves afoot to be able to turn them off to avoid overloading the electricity grid with surplus electricity. 

However electricity bills are kept high by the price of electricity that increases in the mid to late afternoon as air-conditioning loads increase at the same time solar PV output is falling. 

If your business or household is exporting a large amount of electricity in the middle of the day, and paying a large amount for electricity used later in the day, more suitable appliances can be available to save you money.

There are air-conditioning options that can shift energy use from late afternoon, when cooling is needed, to the middle of the day, when electricity from solar PV systems is at a peak. 

An insulated storage tank that holds 3,000 litres of water costs about $4,000 - using a "Slim Steel" water tank, R7.0 ceiling insulation and a garden storage shed - all available at Bunnings. 

Kingspan 3000L Slim Steel Water Tank - 850mm x 1860mm x 2300mm - $2,695

Cooling 3,000 litres of water from 20℃ to 5℃ uses about 18 kWh of electricity - assuming a water chiller with a co-efficient of performance (COP) of 3 is used.

The cooling can be done in the middle of the day using only solar PV generated electricity. 

The chilled water is then available for air-conditioning later in the day - avoiding the need to run reverse-cycle air-conditioners using electricity from the National Electricity Market - where the price can go as high as $15,000 per MWh ($15 per kWh) in some 5-minute intervals.  

Water Source Heat Pumps (WSHP) use chilled water to cool the air in summer, (or heated water to warm air in winter) unlike typical reverse cycle units which rely on external fan assisted condensers to exchange energy with the outside air.