Waste not, want not: and that goes for solar power, too

by Steven Harris

Of the questions that get referred to me from our advice centres, one that has become a regular is: ‘Should (and how do I) go off grid?’.

Sometimes this is because of a misunderstanding that microgeneration means you have to be off grid (it doesn’t). Mainly, though, the question is being asked by people who want to opt out totally from our fossil-fuelled energy infrastructure.

For those of you out there who are dreaming of energy independence, here are some musings.

The first thing I’d say is, what are your motives? In the backwoods of America, or the depths of rural India, off-grid might be your only energy option – since ‘on-grid’ means ‘no grid’ in some parts of the world. (This has led to these places leading the rest of us in microgeneration, it’s the only economic local energy option.)

For the rest of us, though, if you have the grid and choose not to connect, your real result might not be quite what you intended. Yes, you will have opted out of a fossil-fuelled infrastructure for your day-to-day power, but unless you have invented some way to store that power, you will also have opted the fossil-fuelled world out of your lovely surplus renewable energy.

One of the reasons why grid-connected renewable electricity generation is so useful is because anything you can’t use can be squirted back along the wires back into the grid for other people to use. This means that every ray of sunshine that falls on your PV panels can be usefully harvested and put to work.

By contrast, solar thermal systems, although they are very useful, are always ‘off-grid’, and can only heat up a tank of hot water and no more. Unless you use that hot water before the sun goes down, any further sun is of no use and any further harvest has to be… well… dumped.

But if you were to go off-grid for electric, what would you need?

First, you’d need a cupboard full of batteries. This is your electrical version of a hot water cylinder. If you were in India or Africa (or a van or a narrow boat), and were only after a few hours of small power in the evening, this might just be a few car batteries. For your full 21st century home and lifestyle, we are talking  serious purpose-made deep-cycle power cells, often with military backgrounds.

Second, you’d need a means of generating electricity. This can be solar PV, wind turbines, micro hydro and then (essentially), a diesel generator.

And third, you’d need a means of managing and controlling all of this kit so it would be able to give you the sort of power you want, when you want it.

Easy, I hear you say? Well, not really! Get it wrong and your batteries will soon be pining for the fiords, and these sort of batteries don’t come cheap. In fact, the batteries are likely to be the most expensive part of your installation – even more expensive than your PV panels. Also (and this is the killer), you would be doing very well if you got back 70% of the power you put in.

As with mobile phones and the laptops of old, if you abuse your batteries by (say) using them down to the bottom of their charge, or worse still, never letting them charge up completely, soon they will not hold charge, or will hold it okay, but only let you have it back at a trickle. (Those of you with old cordless drills will know what I mean here.)

This is why it is rare to find your backwoods homesteader without also a diesel gennie. This isn’t so much that they can’t rely on renewable energy for their power, it’s more for their battery maintenance regime. They need the gennie so they can do things like ‘equalise the charge’, ‘final float charge’ and ‘fizz off impurities’. Things for which you need an easily ‘turn-on-and-offable’ power source.

So you can see this route isn’t for the fainthearted (let alone the faint-walleted).

So let’s look at on-grid instead.

With electricity from the grid, you don’t have to worry about storing power because anything you don’t use in your home can be pushed back through your meter and down the wires into the local grid. The local grid is practically always hungry for power and will gobble it up in your neighbours’ houses and the community infrastructure.

So not only will you be spared the expense of batteries, your nearest and dearest will be spared your turning into a battery bore. (If you don’t believe this is inevitable, try reading a few articles from Homepower magazine).

But the main point is that the grid isn’t just something you take electricity from. You can actually give some back.  By doing so, you’re helping those who for whatever reason can’t install their own solar panels, avoiding waste, and contributing to the decarbonisation of the grid. In other words, not just avoiding the problem, but contributing to the solution.

And if that wasn’t touchy-feely enough, here’s one last ‘pro-grid’ idea to leave you with. From afar, you could be excused for mistaking a solar power farm for a housing estate, only there are no houses underneath the panels. The builders end up having to build ‘grid infrastructure’ to take the power away to where it can be used. How daft is that? If you built the housing estate under the solar farm, (or put panels on the roofs of housing), the infrastructure would already be there to take the power and you might be able to make use of some of that power before sending off what you didn’t use to supply the world with sustainable renewable power.

Any more questions? Our advice line can help you find the best low-carbon solution for your property. Ring 0800 512 012.