Can I use solar to heat my home?

solar thermal with pv
Can solar be used for heat?

This is a question that I get asked a lot and usually the person is asking if the hot water generated from a solar thermal system can be used to provide heat for the heating system instead of for the hot water tank.

The answer to this is yes it can but it requires a thermal store which, as the name suggests, stores heat which can then be pumped around the building as and when required. This is a great solution for a very large house (e.g. 6 bedrooms plus) or a commercial building but is not suitable for a normal domestic dwelling as the thermal stores are so big (1000l and rising!) that they just aren’t practical or cost effective.

However, solar can be used to heat your home in the form of solar pv. You are probably pretty familiar with electric storage heaters. People who have these usually have a dual-tariff electricity supply where electricity is cheaper at night-usually known as Economy 7. The storage heaters build up a bank of heat by being slowly heated with the cheap electricity at night. The heat is then slowly dissipated throughout the day.

storage heaters
the humble storage heater

The problem with storage heaters is that there’s not a lot of control-it is usually stones/bricks that are heated up within the heaters and you can’t really turn a stone off!  The good news is that this system has been updated for the solar age. With solar pv and battery storage, a large bank of electricity can be built up and then electric radiators used to dissipate heat when and where you want it. They are fully controllable via thermostats and you will have the greatest amount of electricity in the battery when you really need it-in the evening. This is when the storage heaters are usually starting to run out of heat.

For properties who are on Economy 7, the more advanced batteries, such as Tesla, are able to switch between solar storage and mains storage. This means that for most of the year, you can get the benefit of the solar pv stored in the battery, and then for the winter months when solar generation is low, the batter can be fed by Economy 7…the best of both worlds!

So, yes, solar can heat your home! Give us a call if you want a free consultation to see how this could be done for you.

How do I choose a heat source?

Construction site
What heat source would you choose for this place?

Once you have decided how the heat is going to be distributed around your property, the next thing to decide is where the heat is going to come from.

For most people on the gas grid, this is a fairly easy decision. Mains gas is the cheapest heat source available (3-4p/kWhour) and obviously the nice people from British Gas (or whoever) have gone to the trouble of hooking up a gas pipe to your home. Just a little word of warning though. As I mentioned in the last blog, if its a new build and underfloor heating is being used then a heat pump is a real option and should not be ignored. At the very least, get a quote and see how the running costs work out. Also, gas is a fossil fuel and there is only a finite amount of it left in the world. As supply gets more scarce, prices go up. It’s common sense. Maybe now is the time to get on the right side of history and consider a renewable option.

Supposing that you do want to go renewable. There are two main options: biomass and heat pumps. There is a lot to think about with either one of these heat sources. In fact, I have already written a blog on some of the things to think about if considering a biomass boiler. Find it here

Heat pumps come as two main types: ‘air-to-air’ or ‘air-to-water’. An ‘air-to-air’ system is basically an air conditioning system that can be used to either heat or chill the air. Obviously, this has the advantage that in summer it can be used for chilling. If you happen to have solar pv panels too then this is obviously when the solar panels will be working their hardest and providing loads of electricity. You could actually be using the sun to cool your home!

One of the disadvantages is that you have air blowing units in the house which most people don’t like. In reality, they actually run very quietly, similar in noise to a fridge but in every room that can be a bit much. Another thing to consider is that ‘air-to-air’ heat pumps are not eligible for the Renewable Heat Incentive which pays you to generate heat.

An ‘air-to-water’ heat pump uses the refrigerants to heat water for a normal heating and hot water distribution. Heat pumps have something called a ‘Co-efficient of performance’ (sometimes referred to as a ‘seasonal performance factor’). What this means is the amount of heat energy that is extracted from the heat pump compared to the amount of electrical energy that is put into it. A heat pump with a co-efficient of performance of 4 produces 4 times as much heat energy as electrical energy put into it. This modern miracle is explained through the science of refrigerants. I won’t bore you with the details here but just to say it really does work and this makes heat pumps by far the most energy efficient heat source available. Their efficiency can be increased even further by using solar pv panels to provide the electricity which is required to power it. Effectively this makes it a zero carbon heat source. Very exciting!

If you really don’t fancy renewables, then the main options are oil and LPG. LPG is usually delivered but can also be collected in bottles and brought to the property. Oil is almost always delivered and is stored in a large tank in the garden. Price wise, oil is the most expensive even with the drop in oil price that we have been hearing so much about lately. At some point, this will definitely rise, no doubt in connection to the next Middle-Eastern war. Again, my advise is to get on the right side of history and go renewable! One more point on LPG and oil boilers. Their lifespan is usually 10 years or so…15 if very well maintained. A heat pump or biomass boiler will last for up to 25 years! This should be borne in mind when sizing up the cost benefits or these choices.

How to maximise your solar pv-the quick version

tesla powerwall battery
Tesla Powerwall battery

If you are reading this, you probably downloaded my e-book on this topic and then thought, “looks a bit long, I’ll give it a miss.” Because I am the understanding type, and I may have had similar thoughts myself from time to time, I have decided to write a quick version in the form of a blog.

So, in 663 words, here’s how you do it:

  1. When the sun is shining, run about like a nutter turning things on, even if you don’t need them. Obviously, this method is limited. There’s not much point turning the lights on when you could just open the curtains…depending on what you are doing behind the curtains, I suppose. Winking Face on Microsoft Windows 10 Anniversary Update
  2. Get good data. You’ll never know what you are producing unless you have something which tells you in real time what’s coming in off your solar pv panels. Really you need something which will give you a detailed breakdown within specific time periods of how much you are generating, how much importing and how much exporting. With this data you can put together a good picture of when you are producing electricity and this will help you use it most effectively. I am happy to say that such a devise exists. It is called a Smappee and is a little gizmo which attaches to your incoming electrical supply and does all of the above. You can even access your data with an app so you know what’s going on all of the time. Costs £260 from their website. We can give it to you for £236. Bargain!
  3. Get a solar hot water optimiser. This is a devise which is constantly measuring how much electricity you are exporting from your solar panels and how much you are using. As soon as you start exporting electricity, the optimiser will turn on the electric immersion element in your hot water cylinder to match the exported power. Put simply, you get a cylinder of hot water without using up any gas. This is a great little devise which requires no effort on your part at all-it just works! Our installed price for a Power Diverter (there are a few different makes but in my opinion Power Diverter are the best) is £420 including VAT. Another bargain!
  4. Electric cars. These aren’t strictly a solar thing but works well with solar because it is a great way to use up your solar generated electricity on something worthwhile-filling up your car. This will save you tons of cash at the pump and also leave you less reliant on the fuel spikes and troughs that we’ve been seeing these last few years. Obviously, getting an electric car is a big investment and requires a lot of thought but in terms of making the most of your solar pv, its a real winner!
  5. Batteries. The single best way to make the most of the electricity that you produce with your solar panels is to get a solar battery. If you think about it, this is obvious. You generate electricity during daylight hours and the chances are that you are out during daylight hours. The peak load times of a typical house are in the morning and evening-when people are in the house! If you can store the electricity that you are generating and use it later then that is a big deal. Well, now you can! The best battery on the market by a mile is the Tesla Powerwall. This can be easily retrofitted to a solar pv system. Its a beautiful looking piece of kit and can even be installed outside of your house so all the neighbours can look and be jealous. The Tesla Powerwall will store 6.4kW hours of electricity which can be used when the sun is not shining.

If anything in this blog has interested you and you’d like to know more then please go to the ‘Arrange a Consultation’ link on the homepage and we can get together and have a proper chat about how you can maximise your solar pv!

 

Underfloor Heating

underfloor-heating

Next up in this blog series is a few tips for those who are thinking about installing underfloor heating.

There are many advantages to underfloor heating. The main one is that it means that you don’t need any radiators taking up space on the walls. Also, since heat is coming through the floor and rising upwards, you don’t lose heat to the top of the room as can often happen with radiators. This is particularly the case with large buildings that have high ceilings like schools and industrial buildings.

Another advantage is that because having underfloor heating means that your floor acts as a great big radiator, the flow temperature of the water can be kept low which can aid the efficiency of your boiler or heat pump.

Underfloor heating is ideally suited to new builds. The first reason for this is obvious. Installing UFH is much easier when you don’t have to rip up the existing floor to install the pipes as you would on a retrofit. The second reason is that, as mentioned above, the flow temperature of UFH can be kept quite low. This is particularly the case for new build properties, assuming they comply with modern building regulations which basically packs in more insulation than you can shake a stick at. As the property is heavily insulated, you don’t lose much heat and therefore a low flow temperature will work fine. UFH can still be used on older properties but you need to be careful that the heat supply will match the load. A professional should definitely be consulted.

Underfloor heating manifold
Underfloor heating manifold

UFH heating involves laying out and clipping long loops of pipe over an insulated floor covering (this stops the heat going down instead of up). There is usually one loop per room or zone and this is controlled by a thermostat located in that room. The loop is connected to a manifold usually located close to the heat source and the thermostat opens and closes the appropriate valve in the manifold once the zone has reached the required temperature.

Installation of the loops is fairly straightforward for a competent DIYer although care must be taken with pipe sizing and the distances between the pipes. However, lots of suppliers will do a full design for you so it should work out ok. Once everything is in and connected back to the manifold the system must be pressure tested. It is very important that you do this. A concrete screed will cover the pipes. Once the pipes are covered in concrete fixing a leak will involve a LOT of work!

As I mentioned above, UFH works well with a low flow temperature. Care then needs to be taken with the heat source. A normal boiler will heat the water up to 60 or so degrees and then will be blended with cold water to bring it back down to temperature appropriate for UFH. This is particularly the case if there are radiators being added in to part of the building (lots of people go for UFH on the ground floor and radiators on the first and second floors). Obviously, heating water up only to cool it down again is a colossal waste of energy and best avoided!

How can it be avoided? By using a heat pump! Heat pumps operate with a flow temperature of around 40 degrees. This is exactly suited to UFH! If, as in the above scenario, you want UFH and radiators throughout the building, this is still fine for a heat pump as there are many low temperature radiators now available.

People often ask me if a heat pump is financially worth it in gas-grid areas and the answer is yes, if you are installing UFH. With a standard gas boiler, all that heating up and cooling down will lead to high heating bills and inefficient use of resources which can easily be avoided. If its a new build, go for a heat pump with underfloor heating!

 

Radiator distribtion systems

Radiator
What a lovely old fashioned radiator

There are a whole load of things to be considered when installing a new central heating system and I’ll be writing a load of blogs over the next few weeks to discuss some of these. But I am going to start, probably not where you might expect me to-with the heat source, i.e. boiler type, but with the heat distrubution-i.e. the radiators.

This is my starting point because this is what is most important to you. Unless you’re a heating obsessive you probably don’t want to spend your time worrying about where your heating is coming from-you just want to enjoy  being warm. Therefore the mode through which you ‘feel the heat’ is the most important.

If you’re looking for the most straightforward system to retrofit to your property, then you are looking at a wet radiator system. I would say about 95% of central heating systems in the UK are of this kind and this is for a reason-its effective, its reasonably priced and its not massively disruptive to install.

Some people love radiators. They look at them and just feel warm. I once installed an underfloor system (more on that on next blog!) to an old lady who insisted that I put in a radiator as well…not connect it up, just put it in so that she could look at it and feel warm. Madness! (I eventually talked her out of it and she now loves her underfloor system).

But people like radiators because they know where their heat is coming from, can put their hand on it and know its working. And to be fair, they are a great way to distribute high grade heat around a building. Beware though-they are deceptively complex and more thought goes into a well designed radiator system than you might imagine.

First of all, distribution. The pipes need to get from your heat source to your radiators. There is a flow and a return which each radiator connects to. A bit like this lovely diagram.

two-pipe-system

So, where are the pipes going to go? Easiest and neatest way is under the floor. But this will only work if you have a cavity (preferably more than 2′ deep-working on your back installing a heating network isn’t that much fun, believe me!) or floorboards that can be lifted and set back down again. If you have a concrete floor (presumably with tiles/carpets laid down) then this is going to be a major job best avoided.

If taking the pipes down is not an option then they must either go horizontally between the radiators or vertically. A vertical system means having the distribution in the loft and then dropping down for each individual radiator. Either way, this is going to mean that pipes are exposed UNLESS you want them integrated into the wall. This is possible although again will mean some mess. A plasterboard wall is easier as the plasterboard can be cut away, the pipework ran and then replaced and replastered. A stone/brick wall must be ‘chased out’. This is the soul-destroying process of chipping away at the brick until there is a space big enough for the pipes to go in. Once everything is in the pipes are plastered back in.

In my opinion, both of these options are totally unnecessary. The pipes should be boxed in or even made a feature of in an industrial uber-cafe, hipster kind of way. Either way, you won’t notice them after a while and the poor plumber will still have the will to live.

Thought should be given to the sizing of the distribution pipework. i.e. if many radiators are being taken off a single branch then the branch needs to be a bigger diameter pipe (i.e. 22mm or even 28mm) than if one radiator being taken off it. However, a heating engineer should probably be consulted for sizing of pipework as it can be a little tricky.

Sizing of radiators is the next job. You have probably noticed that big rooms tend to have big radiators and little rooms have little radiators. I am not going to patronise you with the reason for this. Radiator sizing is done by matching the heat loss of a room with the radiator’s btu or power rating. Now, this is pretty complicated and I know very few heating engineers who actually do it. They usually just go on experience. This will probably be fine but you may get unlucky. Always ask the heating engineer if he or she knows the heat loss of the room and if the radiator is sized to match. If they try to fob you off then they haven’t done it!

One of the problems with radiators is it really limits the room layout. If a radiator is on the wall then you can’t really put furniture in front of it or it won’t do its job. Ideally the radiator should be made as small as possible. This can be done with double, or even triple radiators. These kind of radiators have more depth and give out more heat for the wall space taken up. These are more expensive but really make a big difference. I would always recommend at least doubles in everything except the smallest of rooms. Another little trick that I see more and more is aluminium foil being placed behind the radiators. This basically stops the heat from being absorbed into the wall and reflects it back into the room. Great for making the most of your radiator but doesn’t look too pretty!

People often ask if copper or plastic should be used. To be honest, either is absolutely fine. Copper is obviously the traditional choice and many plumbers refuse to use plastic. But to be honest, they both do the job perfectly well. Some early plastic fittings sprang leaks fairly easily but you shouldn’t get this problem now. Hep-my plastic pipe of choice-offer a 50 year guarantee on pipe and fittings-you won’t go wrong.

One last little thing which is a bit of a bugbear of mine is the tails to the radiator. I hate to see an exposed plastic fitting underneath a radiator. They just look clunky and horrible. As I said above, plastic is fine but a plastic fitting on the tails? No way! Make sure its copper.

Plastic fittings on radiator tails…ugh!

So that’s a few thoughts on radiator networks. Of course, its not comprehensive and I’d love to hear any questions or comments you have on this. If so, please comment below.