I certainly don’t have my own oil supply.  However, since Susan and I put a few solar panels on our roof a couple of summers ago, we have generated (October 2017) 8.3 MWh and made about £1200 selling what we don’t use back to the grid.  And ours is just an ordinary domestic installation.  Like most things, if we can use bulk buying, and we have houses built to PassivHaus standards (which typically only uses 5%-10% of the energy of a normal house for lighting, heating and cooling) then we can afford more extensive use of solar … and we will use less of the energy.

Solar can be in the form of passive solar (have big windows on the south side of the house), solar hot water, or solar electric. Susan and I have a conservatory across the entire width of the south side of our house, and the sun really doesn’t need to shine all that much for it to get pretty hot in there.  We often leave the kitchen door to the conservatory open, just to let in the warm air.

We used to have solar water heating, but we weren’t impressed, and eventually had it replaced by solar PV (photo-voltaics), plus an Immersun system, and a Thermodynamic system.

The thing about solar electric is: you get electricity when the sun is shining, and not when it isn’t.  So, if you’re all out all day long (work, school, etc) when the sun is shining, then you’re generating electricity … but not using it.  You all come home in the evening and switch on the lights, the computer, the TV, the washing machine and then you’re using a lot of electricity, but you’re not generating any.

Our Immersun system is a way of partly getting over this problem (I did say, “partly”!).  During the day, when the sun is shining, a special controller monitors how much electricity we are generating, and how much the house is using.

Unused electricity is switched into an immersion heater, and it heats our hot water.  You could say that this is a way of storing solar power … except that we can’t get it back in the evening to power the TV!  And when the water is hot, and we are still generating electricity, then it gets fed into the grid system, and we get paid for it (not a lot, and the rates are going down).  At night, when we are using electricity but it’s dark, then we draw electricity from the grid, just like everyone else … but it does mean that our electric bills have gone down.

We have recently (summer 2017) ordered a Tesla Powerwall 2 solar battery so that we can store unused solar power for when the sun doesn’t shine, and, when the sun doesn’t shine for long periods, the battery will recharge overnight using cheap-rate electricity. This sort of technology will be significantly more cost effective when installed in bulk in a village.

Oh, and that “Thermodynamic” system?  Well, in the depths of the winter, when it’s dark and freezing outside, it uses a special sort of air-source heat pump to make sure that we do get hot water.

And that’s probably about as much as we could do, in an ordinary residential house, as a “retrofit” option.  At least, that’s what we thought before we attended the Solar Energy 2015 exhibition at the NEC in Birmingham.

There we learned that solar energy storage is all the rage—and it’s only got more exciting since then, as our order of Tesla Powerwall 2 (above) shows.

Solar Storage

Basically, solar storage is nothing more sophisticated than a set of batteries (they could be lead-acid batteries, just like car batteries, or they could be lithium ion batteries, just like your mobile phone batteries–but bigger) connected up to a set of electronics.  In the same way as Susan and I have electronics to divert excess electricity to an immersion heater, these electronics divert the excess to charging up the batteries.  And in the evening, when everyone is at home, the system uses electricity from the batteries before it uses electricity from the grid.  Then at night, the clever electronics use off-peak electricity (Economy 7) to put some charge back into the batteries.  If the electronics are clever enough they will understand what you use when, and what time of year it is, and what the weather forecast is, to make sure that you have “room” in the batteries if it’s going to be sunny, but that you have power in the batteries if it’s going to be dull.

There are dozens of manufacturers producing solar energy storage systems, from the UK’s Powervault, through Moixa’s Maslow (shown here) to the Tesla Powerwall that uses the same battery technology that powers Tesla electric cars.

So far, so good, but if we are using solar in a whole village, do we just multiply a simple domestic installation by the number of houses in the village?

No, we can do better than that.

Large Scale Solar Collection

We have all probably seen solar farms around the countryside.  I picked up a map of solar farms in the UK and was astounded by how many there are (well over 1000, Oct 2017).  You can get quite a reasonable return from one or two acres of solar farm … and that land is not lost to agriculture.  You can graze sheep, goats or chickens in the same field as you have solar panels (in fact the livestock like sheltering under the solar panels in bad weather!) and Cotswold Seeds even sells special grass mixes for sowing in solar fields, depending on what you want: tough, slow-growing, herbal leys good for sheep, or wild-flower meadows.

And then there are companies that sell special barns with solar roofs, like the Sola+ system shown below.


And, of course, in the village there will be communal buildings, all of which will have roofs, and which can collect solar energy, which can be stored in small-scale, or large-scale, energy stores.  All of which is starting to make the solar energy system look complicated … but, with hundreds of houses, community buildings, retail, hospitality, farm buildings with roofs, car ports with solar panels, and a solar farm, and energy storage throughout, we have enough scale to get consultants in to design the solar system, and what they will probably use is a “micro grid”.


“A microgrid is a local energy system which incorporates three key components; Generation, Storage and Demand all within a bounded and controlled network. It may or may not be connected to the grid. Microgrids (µG)” “Five minute guide”, Arup.

You can think of the national electricity grid as a black box.  Connected to it are all sorts of electricity generating devices, from offshore wind, to conventional coal-powered stations, through solar farms, to nuclear.  Also connected to it are all the people and businesses that wish to consume electricity.  And there are some very clever people who twiddle the knobs and pull the levers to make sure that the supply meets the demand.

Well, a microgrid is just a small-scale one of those, and the control mechanism can be a large complex computer system, or it can be a box on the wall.  And with microgrids, in addition to supply and demand, you can add storage.  The small microgrid could be completely stand alone, with no connection to the national grid, or it could be connected to the national grid.  The national grid could be a supplier, a user … and the national grid could use the microgrid as a storage device.

As you can imagine, the subject can get complex, but today there are microgrids that are amazingly low cost, and which can give Foldehampton a resilient energy supply, and can earn money by providing a degree of resilience to the larger community.

Finally, UK company, Powervault are making storage devices that fit easily into the home, as are Moixa, with their Maslow system.  I am hoping that we can add one or another of these to our own solar installation so that we can evaluate its effectiveness.  (I wrote that in 2015, long before we ordered our Tesla Powerwall 2.)


This short video, although American, gives a good idea of what’s possible with a micro-grid.


Grid Aggregation

If you have an energy store, like Moixa Maslow or Powervault, then you get a number of benefits, including being able to store up the day’s sunshine to use at night, and buying in and storing cheap “Economy 7” electricity at night, to use during the day.  And, of course, if there’s a power cut, then you get a degree of insulation from the effects of that, too.

In fact, what we have given ourselves is an extra degree of resilience.

But there’s an really interesting extra advantage.  This resilience, our resilience, is of value to people outside of our community: the national grid operators.  They have the responsibility of smoothing out the peaks and troughs of supply and demand.  And our battery storage can be of benefit to them.  We can give them permission to store some of their excess generation into our batteries, and to withdraw it when they need it.  Of course, we’re just a tiny drop in their ocean, but as the technology grows, all those tiny drops add up to something useful to them … and they are willing to pay for it.  Moixa have recently announced their “Maslow Gridshare” system which pays £75/year for five years, just for agreeing to be a part of their system–and you get the benefit of being able to store your own solar energy for use when the sun isn’t shining.

Think this all sounds a bit too “future tech” to be true?  Well, UK research company Cenex is working on a system (EFES) where electric vehicles, plugged in overnight to charge their batteries, could be used as temporary storage by the grid companies, to help smooth out their ebbs and flows!  It’s not here yet, but it could be by the time we’re ready to build Foldehampton