I recently moved into a house that was consuming 85 kWh a day through winter. Ouch. I’m working to reduce it but realistically dropping it below half of that might be hard. Philosophically and economically irrationally I want my home to be a net zero consumer of electricity. If I can’t achieve this on a daily or weekly basis then I’ll settle for an annual basis.
Our peak loads will most certainly be in winter when solar irradiation is at it’s minimum, this is our constraint. I installed 10kW of panels and a 10kW inverter to start with. I might over panel it in future.
Thinking about all of the above, and granted storage is rapidly becoming more feasible, maximising self consumption of power from residential solar is going to play an important role in minimising the use of fossil fuel generated electricity.
This blog post is my experience of figuring out how to do this.
Solar system comprises of:
- 36 x Hanwha Q.Cells Gmbh Q.Peak 280W mono modules
- 18 x TIGO Dual Maximisers with independent panel tracking
- 1 x TIGO Single Maximiser
- 3 x TIGO rooftop gateways
- 1 x TIGO MMU or inverter datacard
- 1 x Fronius 10.0kw SYMO 3P Austrian Made PV inverter
- 4 x IMO DC isolators
- When excess power is available, divert power in order of priority to:
- Heat pump hot water 1-2 kWh/day
- Electric car charger, if connected, typically needs ~10 kWh/day
- Pool pump, requires 3/6 kWh/day (winter/summer), ideally run in the middle of the day.
- Storage (if installed in future)
- Air conditioner – during winter and summer only.
- Unit 1: SRD20E : 6.18 kW
- Winter use normally 6+ hours per day.
- Unit 2: TBC seldom used.
- Unit 1: SRD20E : 6.18 kW
- The total demand from the rest of the home is unknown at the moment due to significant recent changes. I’m expecting/hoping it will settle at around 10 kWh per day.
- There’s not a lot around in terms of mainstream out of the box solutions.
- The Fronius inverter has the ability to initiate switching based on excess generation but only on a single circuit.
- A similar approach could be used as this EV owner has setup: https://onestepoffthegrid.com.au/lessons-in-automatically-solar-charging-an-electric-car/
- The Tesla comes with a standard 10 Amp charge connector that will only draw circa 2.5 kW. By leaving this connected over the course of the week the car should receive enough charge. Some manual monitoring will be needed but it can always be topped up with the higher 32 Amp charger.
- http://www.immersun.co.uk/ – website suggests it’s only useful for resistive elements, no mention of heat pumps.
- It’s no use for me but if you’ve yet to install solar an SMA inverter may be worth considering as it can be coupled with their Sunny Home Manager which provides capability for routing excess solar generation.
- Flapping (rapid turning on / off) of power loads is bad for appliances (particularly heatpumps).
- Home automation equipment such as the Insteon gear might be of use.
- PVOuput.org have a website and app for graphing and tracking demand and generation.
- http://solar-log.com.au/ – looks like it will do most of what I’m after. They appear to have a limited presence on the ground in Australia though.
- Zwave, apparently possible with these three components:
- Installed a Fronius Smart Meter, this provides a data feed of power consumption which the inverter uploads to PVOutput.org along with solar energy production data.
- Using the above data from the smart meter I can see that the majority of the time the solar produces enough power to cover the pool pump. I’ve scheduled the pool to run between 10am and 2pm in winter and will extend beyond this in summer.
- Hot water system was changed to a Sanden Heat Pump and has been scheduled to start at 11am each day, typically running for around 2 hours at 1kW load.
- The above two are rudimentary scheduling changes, there are days when solar output is insufficient to cover the load but for the most part it does.
References & Resources:
This post is an ongoing work in progress – check back for updates.