DIY: Get ready for a natural high

DIY: Get ready for a natural high

Kya deLongchamps reports back on the performance of her photovoltaic array and wonders if it could handle the addition of an electric car 

With the new Government-backed climate action plan now on the table, I know many of our readers will be feeling bruised at the full-on assault on fossil fuel-powered, central heating systems and the intention to raise the Carbon Tax to €80 per tonne by 2030.

Under Minister for Climate Action Richard Bruton’s proposals, gas and oil boilers have become public enemy number one, with an “easy pack” set of solutions for retrofitting up to 500,000 extant, underperforming homes on the way by the end of this year.

It’s going to be a complex adventure to answer our carbon responsibilities for the EU, and I suspect the streets will be filled with neon-vested outrage before a compromise we can live with (and pay for) is finally thrashed out to coax us into compliance.

Sustainable source

As I previously reported, we committed to a renewable energy source for our home. We saved for it steadily, considered the choice of technology, and settled on 4.3kW photovoltaic panels married to a 6.5kWh battery. There is also a diverter to supply most of our hot water from the surplus power directly to our standard immersion tank through a dedicated element.

There’s a “boost” facility to draw power to the tank as needed — we have yet to use it. Our capital outlay was grant-aided to the tune of €3,800 through the SEAI. It’s still high summer, but I can now report back on the energy performance results and odd behavioural impact thus far.

Watching our array yield and usage through the Solax Cloud monitoring software that comes with our battery and inverter, the highest daily yield we’ve had on any single day was 22.20kWh (July 15), the lowest being 2.8kWh (June 23).

It’s not a race to the top (half of those 22.20kWh on July 15 went straight back to the grid) — the goal is a steady supply to cover your needs.

Powering on

The array tipped 4kW intake on a few occasions but hovers between 500w and 3.2kW between 9am and 6pm from an east/west split set of 14,300w panels. Our average daily yield has been around 12.9kWh for June and the first two weeks of July, and our daily usage is between 8kWh and 10kWh.

The total power we use from the grid has yet to get above the 2kWh mark daily, and is closer to 0.75kWh. The battery takes over in the evening and is often still quite “full” from the day before, great for dark mornings with thundering rain when the real time performance of the panels trails off.

The system has driven me cheerfully insane. I accept the vagaries of the weather, I cheerfully engage with the technology, and making free power has proved to be (for me) a natural, emotional high that bounds straight over the relatively long payback for the system.

I am at home by day, using the “A”-rated washer/dishwasher and (heat pump) dryer sequentially, using power reactively (if the weather is good) and therefore I’m best placed to make use of a PV system.

We are constantly mulling how we can use, or absorb and retain power in other ways — a battery mower and so on. There’s no escaping standing charges and the PSO levy, of course.

Checking up

The family are suffering through my messianic enthusiasm. I almost drove a Kya-shaped hole in my daughter’s bedroom door when I heard the tell-tale roar of a plug-in blow heater. I banned the use of the 900w vacuum cleaner for three weeks. Finally, I used it, frolicking back and forth to the PC to read the real-time impact and realised that when the sun is up or the battery had juice, there wasn’t a blip in our grid consumption. The electric Triton shower proved to be a watt monster after three minutes — disappointing.

Right now, we are creating 85%-95% of all the energy we use (saving around €60 in four weeks), have free steaming hot water and are still gifting around 2-4kWhs back to the State every day. By 2021 a feed-in tariff (FIT) will allow micro-generators to sell their surplus power. The payments for exported kWhs will be a pittance.

Making cents

Given the price of importing power, if you have PV you should sop up as much as you can in usage at home from an appropriately sized and detailed system. Community “block chain” models sending power house to house, as explained to me by Dr Marc Ó Riain of CIT, now make complete sense.

Electric vehicles and photovoltaic appear to be a perfect convergence — a powerful additional source of free watts for cars already whispering through the commute for a fraction of the expense of diesel or petrol. This would seem especially useful where the car driver is physically present during part of most of the daylight hours at home, and where more kWhs are regularly produced by the array than are used. Any PV user I’ve spoken to has admitted to an intense distain of gifting surplus harvested power back to the grid. Frantic, spontaneous vacuuming rallies around the house and half-load runs of the washer are commonplace rebellion.

Motoring on

With my Eddie water diverter doing such an excellent job, I was curious to know what percentage of the necessary charge for an electric car could come from a reasonably sized array detailed with a further diverter for surplus power in real time linked to an EV battery. Could PV outstrip the savings of NightRate electricity?

I didn’t have to go far to find out, as my 84-year-old father has just such a set-up and utilises at 4.2kW array married to a 4kWh battery, an Eddie water diverter, and a Zappi EV diverter to his 40kW 2018 Nissan Leaf.

DIY: Get ready for a natural high

Being retired, the car is at the house, but then again so are my parents — and they are very power-hungry, with tropical fish tanks, running pond pumps, year round CH and a television on 12 hours a day: 30kW daily winter usage — yikes. Being right on the coast with a fully south-facing array — The Sun King is generally at a marked solar advantage to us. That said, I have a much lighter power load.

Getting back to the car, NightSaver Electricity remains the primary source for charging the Leaf at 11.92c per kW with discounts and direct debit usage (at time of writing). This does not include the PSO levy (€47.34 inc VAT) and slightly higher daytime unit charges demanded of NightRate. My parents use all of the 12-14kWh they make during the day from the PV and currently take in around 7kWh from the grid.

Going the distance

Charging the 40kW Leaf costs €4.80 (NightSaver). The real distance without range anxiety has proved to be in the area of 200km, although €270 with perfect, modestly fast, uninterrupted warm weather driving is possible according to Nissan (ev-database.org/car/1106/Nissan-Leaf). Driving 10,000m/16,000km pa, we estimate he has saved in the area of €930 in 12 months on his former 1.6l diesel van.

The PV working well through a diverter (at say 3kWh) contributes about 20% of the car’s power or 40km of his typical distance from a full charge — plenty for four-five shopping commutes. That said, for someone using the car for work, and already charging the car using NightSaver power and the public infrastructure, the PV diverter route would not make much sense.

Winter’s coming. Will my PV stand the course of dark, wet, short days? I’m not sure. I’ll let you know.


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