Sun power for eco-farm

At  Mur Crusto farm, we have completed the final part of the eco jigsaw: we have a photovoltaic system installed and up and running. After a glitch with the wiring, the very professional MGS got our system operational last week. Below are some photos of the installation. Click on them for full sized views:

 Above are the two arrays of nine Schuco panels on the roof. They are supported by a heavily-galvanised robust steel rail system and connected electrically in series so as to generate anything up to 600 volts DC on a good sunny day. The output power is connected to a massive box, the inverter (see below).

 The inverter and its associated safety switches mounted on the board below it, is really the 'brains' of the system, transforming a variable DC input into AC at the voltage and frequency required to feed it into the National Grid or to power appliances in the house. The small white box on the upper right of the board below the inverter records exactly how many kilowatt-hours of power are generated. Our electricity supply company Ecotricity needs to know the total in order to pay us for the power we have generated. With the new feed-in tariffs, this amounts to 41.3 pence per kilowatt-hour. The power is pumped into the Grid via an armoured underground cable which connects to the meter box of Gwyndy, our holiday cottage, which will now be rendered carbon-negative and so can be truly claimed (as we do!) to be an eco-cottage.

Above is one of the simple but rather clever displays on the inverter which tells us how much power is being generated. You can move backwards from Today to Yesterday to the Week or Month and see all the aggregated totals. These include the amount of money generated - always good to know! - and the number of kilograms of CO2 saved by this particular solar powered installation; the feel-good factor.

Are we now carbon-neutral? I don't know but we've

1. insulated everything we can in Gwyndy and Mur Crusto farmhouse
2. have one economical car
3. installed wood-burning stoves for both buildings with all wood sourced from the farm
4. built a solar heat collecting conservatory
5. installed an energy-saving air source heat pump
6. installed the PV system I've described in this post

I think that's about all we can do...


System details

• maximum power the system can generate under ideal conditions - 3.78kWpeak 
• expected generation per year - 2900kW
• saving in CO2 over 1 year - 1.6 tonnes
• system is based on 18  Schuco MPE 215 PS 05 polycrystalline, photovoltaic panels
  mounted on the south facing roof of the barn
• the solar panels are covered by a 25 year manufacturer’s performance guarantee
• total cost - 16,550 GB pounds
• return on invested capital - 8.7 percent in first year rising incrementally to 15 percent in 25 years. Unlike the stock market, this investment payback is guaranteed and in any case generates far more than money held in a bank savings account
• payback time about 10 years
• annual income from sale of power generated - about 1,500 GB pounds

Heat pump: it's all go

Our heat pump is installed, commissioned and running beautifully. Goodbye oil. Hello clean, non-polluting, efficient heat energy. Yes I know most electric power is generated by highly polluting coal power stations but we source our power from a 'green' electric supplier and, later this summer, we'll be starting the process of finding and installing a photovoltaic solar generating system to more than cover the power demands imposed by the air source heat pump.

The installation of all the new radiators and pipework, replacing an ancient and incomplete system, went as smoothly as it could do. The 'dynamic duo' of Paul Southworth and his partner Clare (Paul is a plumber and electrical engineer) made the whole installation as painless for us as it could be given the scale of the job. And Paul's neat pipework and wiring in of the new highly insulated 210 litre hot water tank is a work of art (see photo).

There was one problem after the initial commissioning: the system ran fine but wouldn't turn off. But Ice Energy were quick to send an excellent engineer who quickly realised the problem - a simple wiring error not picked up in the first commissioning - and had the system running perfectly within 15 minutes.


So we are the happy owners of an entirely new concept in home heating which has the added benefit of attracting payments from the Renewable Heat Incentive from April 2011. The pump is very quiet and  amply copes with all the demands put on it. For the first time in the ten years we've been here we can be properly warm in any room in the house. Coupled in with the passive solar heating we get from the conservatory we built 3 years ago, we now have a warm, energy-efficient house.

Pumping heat

Great incentive:  It's unusual to feel that the government is doing something right but with the Renewable Heat Incentive, they certainly seem to be heading in the right direction in so far as encouraging renewable heat sources are concerned.

Heat pumps away!  Suddenly heat pumps seem a very sensible investment with the proposed incentives of about 7.5 pence returned to the householder per kilowatt hour of electricity expended to power them. So we're going for an 8.5kW Ecodan air source heat pump supplied by Ice Energy.We ordered the pump a few days ago and the first tranche of bits and pieces - the hot water storage tank and various other control devices to be installed by a plumber - are due to arrive later this week. Then it's up to us to modify the antiquated house heating system, currently powered by oil, so that it is ready for the actual installation and commissioning of the pump itself. We've found a plumber who is reputed to be very good and who has actual experience of air source heat pumps. He's paying us a preliminary visit tomorrow during which we can decide what we need to do and what we perhaps ought to do. Because the output water temperature of the ASHP is lower than that of an oil boiler, some radiators may need to be changed to a larger size.

The long road: So this is another step along the long and difficult road to carbon neutrality. The pump does, of course, use electricity but its coefficient of performance is around 3 (depending on the outside air temperature). That means we get 3kW of heat for every 1kW of electricity used. It becomes carbon neutral if we either buy our electricity from a supplier like Good Energy or generate some of it ourselves. We've rejected the wind turbine option for the obvious reason of lack of wind so we're now looking seriously at photovoltaics. The British government are offering major incentives in the form of feed-in tariffs which for us would 'generate' 41.3 pence for every kilowatt hour our PV array generates, either for us or which is fed into the national grid. It is really beginning to make sense to invest money in these technologies... much safer than stock markets.

All change on renewables

In my October post, I gave the impression that the case for the wind turbine was all cut and dried. It wasn't, as it turned out, and was a lesson to me on accepting real data as real. I had very much wanted a turbine for two reasons: 1. when the wind blows strongly, it's generally the time you need energy; 2. our location in NW Wales should have been pretty good for windiness. This latter assumption was strongly backed up by the two national databases of wind speed averages and predicted power output. The latter, as it turns out, was wildly optimistic.

NIMBY neighbours do us a favour: We had a tense meeting with our downwind neighbours, arranged to test the waters before formally applying for planning permission. They were implacably opposed to anything visible or audible and I found myself having a little sympathy with their views such that we agreed to go back to the drawing board and see if there were alternative sites or just alternatives. So, Val and I had another look at the results for the average wind speed yielded by the anemometry; the real data. I had previously suspected the anemometer of under-recording wind speeds and, with this in mind, we had checked its calibration by holding it out of the car window at different speeds on a calm day. It was spot on.

And the real average wind speed? I had two results from the anemometer read-outs. One was the average wind speed and the other was the average gust speed. I had - wrongly as it turned out - assumed that the true average would be the average of these two averages (the 5.1m/s figure I quoted in the earlier post). I was always worried about this assumption and had made efforts to find out the correct position, so I posted a question of Green Building Forum and Val phoned an anemometer company and discussed the issue with an expert. The upshot of Val's chat was that we should totally ignore gusts! So that means that the windspeed on my best exposed site in windy north Wales is a paltry 3.58m/s, averaged over almost 12 months! So a wind turbine is out for the best reason of all: there really isn't enough wind on this site. The anemometry and neighbours' complaints saved us from jumping to the conclusion, fostered by the databases I mentioned above, that windpower was for us. So we are saved from acrimonious disputes and almost inevitable planning rejection, from appeals and from building a 25k pound white elephant!

So we're now looking at photovoltaics for which no planning consent is needed. Feed in tariffs of around 36 pence/kWh make this a viable option.

The moral of this story: If you're thinking of putting up a turbine, do the anemometry and believe the results!