Grid Parity – we’re there – sort of.
Grid parity for Photovoltaics – when PV panels make electricity as cheaply as the grid does. It was inevitable that the lines for falling panel prices and rising energy costs would cross and grow wider apart from then on. On the production side this was reached a while ago; renewables beat power stations. For domestic consumption my definition of real grid parity is when it pays to borrow the money to buy the kit that replaces the mains supply. Well we are there now and the implications of this seemingly innocuous bit of news are profound; we are entering the era when it actually makes sense for some people to ditch their main supplier and go off-grid. The off-grid scene is no longer the province of hippies and eco warriors, it is now yours.
Last year grid parity still looked a way off but there’s been a change. Panel prices have fallen to a level in line with the second hand ones I was on about last year, £105 for 275W for example. And the big event is the arrival of a price busting bit of control electronics.
All In One Outback Inverter MPPT SPC III combined charge controller and inverter. This controls the charging of the batteries and supplies 240v ac in a computer friendly sine wave. The 5kW version comes in at around £1,000 and enables Bimble solar to offer a full off-grid kit for £4,533.50 with batteries and 14 275W panels (3.85kWp). N.B. Note the rather low input power. While we recently featured a quite useable 1.2kW system, which runs lights and a fridge and the odd extra, this 5kW one will at least spin up some home appliances but compared to the mains its utility is a bit light weight.
Of course parity depends on the price of the electricity being replaced and whether the PV electricity generated is used. Surplus power can be routed to an immersion heater, car charging or aircon so it is possible to have a system where every Watt is banked.
So. Starting with a £5,000 investment for the kit. Sainsburys Bank wants £91.05 a month for 5 years to pay it off. After 5 years you should enjoy free power for another 15 years or so and freedom from rising prices too. This apparent no brainer deal is tempered slightly by the fact that after every 7 – 10 years the batteries will need replacing; the ones on our sample kit from Bimble cost almost £1,000. That sounds a lot although £12 a month put aside has it covered.
In expensive but sunny Italy, where a Kw hour costs a third of a Euro, our 14 panels should generate 4,355Kw hours or about €120 worth a month. So yes, in Italy, grid parity has arrived and freedom from price rises for many years will make this a sound decision; no more complicated bills and compulsory TV licence either. Anyone building a new house or renovating should give off-grid serious consideration from the start. This is mainly suitable for ex-pats not paying tax in Italy; tax payers should still check out the grid connected route now that there are substantial price falls in panel prices.
Back in cloudy England our panels will be less punchy and electricity only costs about 14p per kW.hr. The chances are that after 5 years you would still be out of pocket by about half the investment and needing another 4 or 5 years to break even, and there will have been a £1,000 battery hit too. Even so, that leaves another 10 years or so of free electricity and with prices likely to have doubled by then this isn’t at all a wrong move. So yes, grid-parity is here but not the hugely compelling no-brainer that will start a mass exodus from the grid.
Grid connected system
Almost shocking price falls make a grid connected system worth a look. The kit does away with batteries and charge controllers; just panels (say 14 at £105) and an inverter (4.2Kw Growatt Inverter 4200 MTL-S Dual MPPT £515). So £1,985 plus fitting gives a chunky (but day time only) power source which, according to The Energy Saving Trust, will give annual benefits of £370. Sainsburys want £70 a month for a £2,500 loan which is too expensive (24% apr) so you’d need to look around or use your own money for a tax free return of 14% for 20 years. Your capital is sunk but even so this is a good return and ahead of grid parity.
If on-grid takes your fancy then you need to call your local MCS approved suppliers to see if you can get registered before 31st March 2019 when the FITs scheme ends.
Now that the lines have crossed, PV deals of all sorts can only become better as time rolls on – watch this space. Note that off-grid systems are surprisingly simple and fairly DIYable whereas on grid systems need a certified expert to install.
PV – overclocking
You can improve the performance of computer chips by overclocking them and, although there is no particular similarity, the same name is used for overpowered PV systems.
Usually charge controllers and/or inverters match the input power of the panels, but as most of the time the panels do not make their full power it pays to have a bigger array – maybe 30% bigger, say a 6kW system with an 8kW array. On those rare sunny full-power moments the electronics will limit the excess input power by what is known as clipping. Most of the time though the system runs in the more efficient part of the power curve turning bad production days into something useful.
A further tweak that really suits overclocking is to tilt up the panels to a winter biased angle. Panels look at the sky and overall light levels so 45 degrees is a good winter angle. This tilt fattens the shoulder months and tempers the power in the summer where the peaks would be clipped anyway.
So the overclock and tilt concept gives much better utility at the expense of overall production but this doesn’t matter where there is no FITs return to consider.
PV overclock and tilt
Dotted red line – where clipping tends to limit production; not a straight line in practice.
Blue line. kW.hrs per month produced by a 6kW array with a 20 degree tilt – no clipping.
Grey dotted line. 8kW array still at 20 degrees – not a great winter gain, high summer clipping.
Red line. 8kW array at 45 degrees – big winter gain, minimal summer clipping.
Note the significantly wider shoulder months and winter production almost doubled.
N.B. Tracking panels grab morning and evening rays so they absolutely love overclocking.
The sun tracking garage loves overclocking.
Solar thermal panels – a bad week?
Our overclocked array almost certainly knocks out the viability of solar thermal panels ( the wet ones with fluid pumped round.) A few more PV panels now have a similar cost to a full solar thermal set up. In winter, when we need to finesse all our kit, the wet panels are often connected to a hot tank so they don’t even run at all. Meanwhile PV panels will still be involved in the plot by running a heat pump (output 3 x input) or an immersion heater. PV plus heat pump is the future. In the summer the PV panels will be over producing so there is no need for another system.
The only way to justify wet panels could be to run my ‘solar stripper circuit’ as on the eco- heating system here. I’ve been running this circuit for years and it is wonderful to see the solar panels running almost every day of the year even when paired with the log burner.
Wood burning stoves – a bad week?
The Government Clean Air Strategy had some bad things to say about stoves and they were right. A stove running cool and with wet wood will emit a lot of smoke with particulates to match a diesel truck. However – properly designed stoves, running hot and burning dry wood, are so much better; the stoves I supply can even be used in London.
Trees are generally good for the environment but when they die or are used for some purpose there will inevitably be wood to be disposed of. If left to rot there will be no particulate emissions but there will be no return for the grower and less incentive to plant more. Any clampdown on stoves could lead to less tree planting and wood going onto bonfires – both disasters. As open fires, both outside and in the home, generate huge amounts of particulates it looks as though stoves are actually the answer, with all that lovely heat and light helping to keep the air clean.
I know that the open hearth is still a popular feature but this particulates argument adds another reason to upgrade to a stove. The other reasons being that open fires burn about 5 times as much wood for the same heat and when it gets really cold the replacement air can make an open fire go negatively efficient. Air conditioning in winter!
That’s all for now. If you need advice, a stove or a heat bank in UK, France or Italy please contact me.
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