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  • Writer's pictureDean Anthony Gratton

A Brighter Green with Air Source

Happy New Year! I hope you all had a wonderful Christmas and an excellent start to 2019.

It’s time to retire the GEC NightStor

Well, for me, Christmas dinner was somewhat in doubt, since the wife (Sarah) and I, in our profound wisdom, decided to have a new kitchen fitted. Unbeknown to us, something we found out later when all the chaos came to a conclusion and the dust literally settled, was that the neighbors were taking bets and the odds weren’t in our favor!

It wasn’t just the new kitchen we were waiting for either – yep, we also plunged into having a new heating system installed – all just before Christmas. Honestly, it seemed a good idea at the time! You might recall from my earlier column, “Sustainable energy: Switching on the community” that a GEC NightStor 100 was used to warm our home and an immersion heater was used to heat the water. The NightStor 100 is a costly unit, which drew a lot of energy for very little output and it was time for it to go. 

Reducing carbon emissions with renewable energy

Sadly, the neighbors were right by the way, we didn’t get to have Christmas dinner in our new kitchen, since the fitters couldn’t install the worktops, plus certain products we had chosen were no longer available, so we had to eat out on Christmas Day. Thankfully, we did have heating and hot water, courtesy of our newly installed air source heat pump, so it wasn’t all doom and gloom! 

You may recall that I started my journey with “green” a few months ago with my solar panels and I’m really witnessing the saving that they are making on our electricity bill – the combination of solar panels and batteries have provided an awareness of how Sarah and I consume and use electricity in our home. But now, I have advanced to another shade of green – in fact, it’s bright green! Having the new air source Mitsubishi Ecodan 14kW unit installed, along with its 210 liter cylinder and all the necessary gubbins wasn’t cheap, but the hefty cost is eased somewhat by the UK government’s domestic Renewable Heat Incentive (RHI). Essentially, the government reward homeowners who choose an alternative energy source to heat their homes and water. It’s their long-term plan to reduce the UK’s carbon emissions and to meet its renewable energy targets. 

Air and ground source options

So, the actual reward is based upon how eco-friendly your house isn’t and our current Energy Performance Certificate (EPC) rating is an unhealthy “G-13.” As such, our RHI should be quite favorable – possibly up to £1,500 a year for the next seven years (all tax free), which will begin to fill in the meteoric dent in our bank account; but that’s only if we qualify. You see, the government mandates several rudimentary requirements that the property owner has already fulfilled, such as cavity wall and roof insulation. With these requirements in place, then you can move forward with your RHI application. Sarah and I should qualify, since the overall energy consumed to heat our home and water is predicted to be circa. 40,000kWh per annum despite choosing renewable energy. The focus is about reducing our carbon footprint. 

Air source works by absorbing heat from the outside, even if the temperature is as low as minus 20 degrees Celsius. The heat captured is absorbed at a very low temperature and passed through a compressor, where the temperature is increased. Air source wasn’t the only option, and we could have chosen to go the “ground source” route, using a similar method to air source but, instead, heat is captured from the ground.

An eco-friendly setting

The Ecodan unit is quite a beast and the coefficient of performance (CoP) rating is favorable at circa. 4.3 – this relates to the consumption it uses versus the actual output it generates. In other words, for every 1kW of electricity it consumes, it would, in turn, generate 4kW of energy. Well, this is all fine, but it’s proving quite energy hungry in terms of electricity, as the unit consumes between 3kW to 6kW an hour to generate heat. On a particularly cold day, any home will inevitably lose heat but, for us, this loss is further compounded due to our home being poorly insulated and our windows being largely single glazed. All this has a dramatic effect on heat loss and, as such, there is an expected additional effort needed from the Ecodan unit to maintain the property’s temperature. I’m confident that the demand on energy will reduce once the fabric of our home has absorbed enough heat within its core. 

Of course, the unit doesn’t always consume such high wattage over the hour, plus I do have the solar panels and battery installation to help ease grid usage. Incidentally, our temperature setting is an eco-friendly (according to our new Nest thermostat) 16 degrees Celsius – we have been without heat for so long that we find anything higher than this to be uncomfortable. I did speak with family and friends to understand their typical settings and they quoted a range of between 20 and 22 degrees Celsius – crikey, I think Sarah and I have seriously acclimatized to the cold!

Using weather compensation to intelligently heat your home

The unit works incredibly hard to reach room temperature and, in doing so, has to consume quite a bit of electricity to deliver heat, but once the Nest thermostat confirms with the heating system that it has reached our desired temperature, then the unit ceases and will only kick in when the temperature drops. In a similar manner to a refrigerator, the heating system only engages when the room temperature has suitably dropped, so it’s not frequently cycling on and off which, in turn, is a more efficient use of the Ecodan heat pump.

What’s more, the Ecodan unit and its central hub (the brains, if you like) is a tad smart, in that it uses a technique called “weather compensation” which, of course, is not unique to Ecodan but all types of oil and gas boilers. It takes into consideration the temperature of the heating system, the set (Nest) temperature from the thermostat, along with the outside temperature where it ascertains if it needs to kick in the heating to generate further heat. However, if the heating system’s temperature is too close to the set temperature, then engaging further heating is deferred for a longer time, in turn, reducing the need to restart the heating. Similarly, the system will also determine how hot to make the water in the radiators based upon the external weather; for example, on a particularly cold day the heating system will increase the temperature of the water whereas, on a milder day, the water doesn’t need to be as hot.

Until next time…

The Ecodan unit heats our water and maintains it at a steady 50̊ degrees Celsius. Using a similarly methodology to a combination boiler, the system heats the water and once the temperature has been reached it then resumes the heating across the home. And, every Monday at 3 a.m. (using the immersion heating on the Economy 7 tariff), the water heats to 65 to kill off any bacteria within the cylinder. But, for me, the most refreshing part of the hot water experience is mains-pressured hot water. Yes, I know it’s a first world problem, but to have mains pressured hot water – wow, what a joy! 

So, we had hot water, a warm and toasty house over Christmas and the New Year and there was no need for our, now packed away, Starsky-esque cardigans to keep us warm – we have heat!

Oh, and as for the fate of the GEC NightStor 100 – well, it was recycled. The chap who came out to decommission and remove the unit salvaged numerous parts and said he could put them to good use elsewhere in other similar installations that are (incredibly) still in use today! I can literally swing the proverbial cat in our utility now that it’s gone.

So, this is where a “what will I do with all this space” Dr. G signs off.

Originally published in Technically Speaking.


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a technology influencer, analyst & futurist 

I dispel the rumours, gossip and hype surrounding new technology

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