PERFORMANCE OF A LARGE DOMESTIC SOLAR POWER SYSTEM

This post describes the performance of a large grid connected domestic solar power system.

Introduction

My solar power system comprises 24 Sunsaver PV panels with a capacity of 4.2 kw and a Sunny Mini Central inverter. The panels face North and are fixed at 60 degrees of horizontal and are free of any shading by trees. My system was installed in 2010 and the meter that could record feed-in kwh was installed in July. This means that at the time of posting the system has had about 8.75 years of operation and has produced about 40,000 kwh. “I like to say 40 million wh because it sounds more impressive.” This equates to an average output of 12.4kwh/day which is quite good when my average usage is normally less than 4kwh/day. It meant that there was a lot of kwh’s available to feed-in to the grid (at 60-71.1cents/kwh) and credits to pay the system off.

System performance

It has made me a net exporter of energy and I have paid nothing for my electricity or my supply charge for many years. I was an early adopter with my solar power system. This meant that I paid a higher price for the system than I would have today. However, this cost was offset by a substantial grant for early adopters. We were also rewarded with a premium (minimum) feed-in tariff (PFIT) of 60 cents/kwh for the electricity that I feed back into the grid. The PFIT ends in 2024. This means that the system has; paid for itself (and more, as it will probably fund my battery storage when the PFIT ends), given me free electricity, paid my daily supply fees and at the same time has saved a considerable amount of greenhouse gas production.

Other electricity reducing factors

When I installed solar power I became much more aware of my electricity usage and found ways of using less and using it smarter ways. I have found that most other PV advocates have had a similar experience.

At the time I installed the solar PVs I also installed solar hot water. This is described in another post solar hot water. I chose to start running the solar HWS with the electric booster switched off as a trial. It worked so well this way that I do not regularly use the booster. Consequently, my reduction in electricity use for hot water was considerable, as was my overall electricity usage.

My home is heated with a central wood stove that is run on fallen trees from my farm. In winter I use it to supply boiling water and do slow cooking in three pots. “Firewood is a very efficient source of heat as it heats three times when you; cut & cart it, split & stack it and then burn it.” 

Because I have a 71.1 cent/kwh feed-in tariff it makes sense for me to use as little electricity as possible during daylight and perform other electricity consuming tasks like pumping water, washing and dehydrating food at night time and preferably between 11:00 pm and 7:00 am when I have an off-peak input tariff. All this will change when my premium feed-in tariff runs out in 2024. 

Other observations

My highest kw power output from the panels happens at midday on clear cool winter days. I think this is because the 60-degree angle of the panels is best suited to winter sunlight interception and also the panels work best when cool. 

I hope that by the cessation of PFIT that battery storage will be a mature technology and affordable. Batteries such as Gelion zinc bromine may fit the bill if they can be kept to their price target “….applications ranging from residential to grid, at a cost of below $100/kWh by the end of 2021.” 

Tim

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