What’s Watt – Living both On and Off Grid – Part 2 – Creating an efficient renewable heating system

In the last part of our Living both on and off grid series we mentioned the importance of insulation when creating an efficient eco home, this is especially important when choosing an Air Source heat pump as they work on lower temperatures than standard gas or oil heating but run for longer at these lower temperatures maintaining the house at a constant pre-programmed temperature, this means they have to work a lot harder and run a lot longer if the house is badly insulated. It is possible to have a heat pump in a home which hasn’t got that good insulation but it means the heat pump has to be upped in size, a detailed heat loss should always be carried out to determine what size heat pump is needed and in the case of a house which is not suitable for this type of heating it will show up in the calculations. ashp-diagramAir source heat pumps work by absorbing heat from the outside air in the same way that a fridge extracts heat from its inside, you could argue that heat pumps are not exactly renewable as they use electricity to run however the heat they extract from the ground, air, or water is constantly being renewed naturally and they are the most efficient way of using electricity for heating as they can typically produce 3kWs of heat for every 1kW of electricity used. You may wonder how they can get heat from the outside air on cold days but heat pumps can extract heat from the air even when the temperature is as low as -15° C. We use an 8.5kW Mitsubishi Ecodan heat pump and it heats both our underfloor heating, upstairs radiators and hot water.

 

One thing to note about heat pumps is they are not suitable for homes with no grid connection, we have one on our property as we are only off grid part of the time and we have connected the air source so that it is separate to the off grid/battery back-up system and constantly connected to the grid. This does mean that in the event of a power cut we would be without the heat pump however we would still have our 9kw wood burning stove with back boiler for hot water and space heating, if it was too warm for the stove in the spring/summer months we would then have solar heated water from our 5.5kWth solar thermal evacuated tube array, so we shouldn’t suffer too badly!Home using a combination of log burner & Solar Thermal

We did get to put the system to the test after the 2012 storms as we were without mains electric for 3 days, it was February so the solar gains for the PV and thermal hot water systems were minimum however we had the back-up generator. We had the system running automatically so that the generator would be brought on whenever the battery bank got low, we used the stove for heat and hot water and the batteries for lighting, fridge, freezer, washing machine etc.  So inside the house you wouldn’t of even known there was a power cut! We’ll go through the PV/battery backup side of the system in more detail in the next blog. For cooking we went with a LPG gas cooker as this is always the best option if you plan to run your home off the grid for any length of time.

One thing to mention when going for an energy efficient system like ours is the importance of sizing the thermal store correctly, the thermal store is the central tank or cylinder where all the heat you’re going to produce from any solar thermal, log burner or heat pump is going to go so get this wrong and you’ll have problems; if the tanks too big for your renewable capacity you’re not going to have enough output to heat the tank conversely if  your tanks too small you’ll have problems getting rid of the heat produced. You can read more about the sizing thermal stores here.

We have a 450ltr thermal store which is quiet large for our house size but we have maximised the roof space and filled it with PV and solar thermal so we needed a large tank, we also make use of an immersun unit which feeds any ‘spare’ electricity being generated from the PV system and automatically switches on the immersion heater on the thermal store. Immersun units work fantastic with PV systems as it means you can benefit from hot water as well as electricity, we have ours set to heat up the top of the tank first just make it more likely that there’s always hot water available.

As you can see there’s a lot to think about when designing a house which can run both on and off grid and the best advice we can give is to spend time at the beginning getting heat loss and projected electricity consumption calculations correct this will be time well spent as should save you from any future problems that may arise.

In the next blog we’ll go through the electric side of the system – PV, Battery back-up and back-up generator and how to integrate the different renewable technologies to make the most out of your system.

Living both On and Off Grid – Part 1

Off Grid Installation at Zip World

Now and again a job comes along that is at once both exciting and challenging, one such job was that of an off grid installation at Zip World’s Velocity site, located in Bethesda in North Wales Zip World Velocity is the longest zip line in Europe and the fastest in the world. The launch site for the zip wire high up in a disused quarry relied solely on an oversized military generator to supply power for the electronic gate system, camera’s and IT equipment. Zip World approached us at Remote Power UK to design and install a eco-friendly and less noisy off-grid system to replace the old generator.

Zip World Velocity Off Grid Installation
Zip World Velocity Off Grid Installation

We first asked Zip World to gather data together of everything they wished to power and then we designed a system which would meet their needs. We went for a 1.5kWp PV system using the REC Peak Energy Solar panels, a Rutland Furlmatic 24V micro wind turbine feeding into a Rolls Solar AGM battery bank, supplying power to a Victron Easy Solar 1600 inverter/charger which supplies mains electricity has a built in charge controller for the PV system, charges the batteries and also controls a  Hyundai 5.2kW ‘Silent’ long running back-up generator which is brought in automatically when the conditions are not favourable for renewables.

We installed and commissioned the system back in October 2016 and we are happy to say it’s been a success so much so that we have just installed a second similar system at Zip World’s Alpha site.

Zip World Alpha Site
Zip World Alpha Off Grid Installation

 

What’s Watt – Living both On and Off Grid – Part 1 -Creating an Energy Efficient Eco Home

 I’m not sure if many people realise but it is actually possible to live in a home which is both grid connected and ‘Off the Grid’ Why you may ask would you want to do this? Well the answer is simple you get the best of both worlds, the security and  unlimited power of being in a  grid connected house with the knowledge that thanks to your off grid system you will never again have to suffer from a power cut!

Running an off grid system alongside a grid connected system means that you make the most out of any renewables you have installed and potentially when conditions allow even run your house completely for free both day and night! This is achieved by using a grid tied PV system to run the house during the day whilst at the same time running a separate off grid PV system which is charging batteries ready for night time use so they are fully charged and ready to switch to off grid mode on an evening and run your house for free using the sun’s energy even at night!   (For winter months we use a back- up generator to keep the batteries topped up)

This may all sound a little complicated so in the next couple of blogs we will run through the set up needed to run a successful on and off grid home. Rest assured this system has been put through its paces by us here at Remote Power UK as for 5 years now It has been installed on the house next door to the showroom and office that owner Graeme shares with his partner Kate. After 5 years of living with the system we can both honestly say it works fantastically well and has helped us make a warm and comfortable home with very low running costs.

So first things first here’s how we went about it – Moving into the property in 2011 we were faced with a badly insulated solid stone traditional built Welsh cottage fitted with only oil heating – about as far away from an energy efficient Eco home as it was possible to be! So the first thing we did was strip everything back to the bare bones, that meant plaster off and floors dug up! We then encased the house in 50mm Kingspan on the walls and 75mm Kingspan in the floor – even though this is a costly job the future pay backs are well worth it as you’ll find the finished house needs very little heat to keep it warm saving you money year on year.

 

One problem with eco homes can be fresh air flow due to there air tightness, to solve this problem its always advisable to install a warm air heat recovery system, this will ensure you always have a flow of clean fresh air circulating the house without having to lose those valuable kilowatts of heat! The next big job was to put in underfloor heating throughout, underfloor works really well with a renewable heating system and we planned to install an Air source Heat pump, Solar Thermal and Log burner with back boiler so underfloor was the best option for us especially as we had already had the floors dug up to insulate.  I will leave you at this stage- in a house reduced to near rubble and cooking on a camping stove – it was all worth it in the end though at the time it didn’t always feel like it!

Join us in the next blog where we will go through the heating system in more details.

Save

Save

UK Renewables hit milestone in production

100kWp System Oxford-Installed by Raine or Shine ltd

It was great to read the BBC’s environment analyst Roger Harrabin’s recent article stating that ‘Renewable sources of energy have generated more electricity than coal and gas in the UK for the first time.’

The National Grid reported that, on Wednesday lunchtime, power from wind, solar, hydro and wood pellet burning supplied 50.7% of UK energy!

It would interesting to know how much of that was generated from Raine or Shine & Remote Power UK’s systems, after 12 years installing renewables hopefully we made a decent contribution!

Wednesday lunchtime provided the perfect conditions for renewables, it being sunny and windy at the same time, what a shame our current storage capacity in the UK is so low as at the time of Wednesday’s record, only 1% of demand was met by storage;

The problem is that our national grid is unable to respond quick enough taking too long to power down the fossil fuel power stations, which is a shame as when the wind blows and the sun is shining these cannot readily be switched off!

If we do want a really effective low carbon national grid for future generations, storage will have to play a major part in the energy mix.

Source- www.bbc.co.uk –read Roger Harrabin’s full article here