Renewable energy at Lackan – some common questions
Here at Lackan Cottage Farm we don’t have a mains electricity connection, and rely entirely on solar photovoltaic panels and a wind turbine to provide power. These charge a 24 volt battery, and power from this is fed through an inverter to produce 240v ac power that runs the houses as normal. When the batteries become fully charged, excess power is used first to heat domestic hot water in one cottage, then the other, and then when they are both hot, we have a couple of electric heaters that come on to use it up. The ideal is that we use all the power we generate in a useful way.
So in summer, and on very windy days we typically have more energy coming in than we would normally use, and so we would take the opportunity to run a distiller to provide water for our batteries, or we’d run the washing machine. Living as we do, we’ve learned to save energy intensive things until there’s plenty being generated, and to be a bit more frugal when the weather is dull or still.
Q – Do you have to do without?
The answer is no. We still have a fridge, a freezer, a washing machine, computers and pretty much any typical appliance. Other than immersion heaters to use up surplus electricity we don’t run energy heavy items such as an electric oven, kettle etc, and there are easy alternatives to those. Certainly we don’t do without, although we do ensure that we can have all the basics such as cooking, hot water and heating without the need for power should the need arise.
Q – Isn’t this all really expensive?
Yes and no. Certainly we’ve found that with electrical equipment such as inverters and charge controllers, you get what you pay for. We started out with cheaper smaller kit when we only had a tiny budget and we’ve updated it as we’ve gone along. About half of our solar panels were previously used – we got them off a Church in Belfast that was changing its panels for newer ones. They work perfectly, and we have the room for them. Our wind turbine is also second hand and we swapped it for some work. There’s no getting around the fact that our inverters, charge controllers and batteries were expensive, but they will last and we have a reliable source of power and no ongoing bills. We’ve also built the system over time as our needs and expertise have developed. So there is the potential for buying second hand equipment – Bimble Solar in the UK sell used solar PV panels, and you can pick other kit up on ebay or gumtree.
Q – It looks very complicated. Are you an electrician?
The current version of our setup is pretty involved, yes, and I’ve had a couple of electricians who are unused to working with DC equipment tell me that they wouldn’t know where to start with it. I’m not an electrician, but I’ve always had an interest in electricity and electronics and some previous experience. As with all these things I bought a number of good books when I started here – CAT do some useful titles.
As with most of these projects I started with small inexpensive equipment that I could make mistakes with, without costing a fortune or endangering my life, and worked up.
Q – I want to go off grid. Should I?
There was a time when I’d have said yes, but now I encourage people to keep the grid connection and view the grid rather like a battery. If you install enough generation and storage to get you right through winter, you will spend a lot of money to cover the worst two months of the year, and then have big surpluses in summer. You are also limited in what you can use by the size of your inverter. If however, you keep the grid, install a good amount of generation and sufficient battery storage to cover your average needs, then when the weather is bad, or you decide you want to plug in a floor sander or some other huge appliance, you can simply draw a bit from the grid without having to worry. You will use the minimum from the grid (and thus have small bills) and may at some point be able to get paid for what you feed back to the grid, though this is likely to be more trouble than its worth.
Q – I have existing solar panels but still have no power when there’s a power cut, even on a sunny day.
Yep. This is because a)you’ve no storage, obviously, and b) because your grid tied inverter will only operate if it sees a voltage from the grid. This is so that should there be a fault with the grid, your PV or wind generator is disconnected from the grid by a physical internal switch and there is no danger that some poor soul working to fix the lines isn’t electrocuted when the sun comes out and shines on your panels. This is the same for all common grid tie inverters.
Fortunately you can install an inverter that grid sense and draw on battery power too. Then you can create a system that prioritises battery use, and only draws on the grid (or feeds back) under certain specified circumstances. This is obviously a more complex system that a standard grid tied installation.
Q – Don’t solar panels, wind turbines, batteries and equipment all have a huge impact on the planet?
They do. There’s no getting around that, and no easy answers. Buying used equipment helps to some extent. The golden rule is to consume less in the first place. Solar panels will last a very long time – 20 to 30 years and more probably. Wind turbines less so, because they have moving parts. Batteries have a very finite life but materials are typically heavily recycled (in lead acid batteries, anyhow).However, all this stuff relies on extractive industrial processes and we can’t simply replace a damaging oil powered grid with a renewables micro grid that relied on oil to make it. There are no easy answers. For us, its knowing that once installed, the equipment isn’t using any more oil, and that we are in control of our own power generation. That of course means it is our problem if it breaks down.
I want to know more. What exactly is the setup?
Our system is divided into several parts. We have 4 solar arrays totalling 9.2kw. 3 of these are run through Victron BlueSolar MPPT charge controllers to a large 2000Ah tubular plate forklift battery. It is connected to two, 3kW Victron Multiplus inverter/chargers that are connected in parallel to form a single 6kw inverter. The output from this is then connected to our house via a standard consumer unit.
One 4kw solar array feeds into a big Grid Tie mppt contrpller/inverter, which is in turn connected to the AC output of our inverters. Thus it thinks they are the grid and becomes active.
We also have a 3.5kw Bornay wind turbine on a 15 metre guyed mast. This is connected to its own huge MPPT controller that feeds direct to the batteries. Its new, and replaces an old grid tie inverter setup so we’re just ironing out some minor issues but it basically works well.
We also have a load diverter that looks at what is coming from the wind turbine and 4kw PV array, and sends most of it to a couple of immersion heaters. Once one is turned off by its own thermostat, the other kicks in until all the water is hot.
To monitor it all we have a Victron BMV712 battery monitor, and also a Victron Color Control unit that allows us to access all the system details remotely over a network. The system also contains a variety of isolation switches and fuses.