PeterW Posted January 21, 2018 Share Posted January 21, 2018 1 hour ago, Jude1234 said: Another newbie question what are the differences between immerson and Sunamp? Pros and cons? By the sound of it to my basic understanding they both use excess solar PV to supplement DHW heating. Both very different ..!! immersun uses the excess PV to use a standard immersion in your hot water or unvented cylinder to heat the DHW when excess is available. The storage media is the water itself, and you still need a primary heat source (ASHP, Gas, Oil, E7 etc) to heat the water when there is no sun. The Sunamp contains all of the above in a single component and uses a phase change material to store the excess PV, and uses E7 currently to heat when there is no sun. DHW is provided when cold mains flows through the heat exchanger and the phase change material releases its heat to warm the water. To compare the cost of both you need to add in the cylinder cost and other controls against the Sunamp pricing. 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted January 21, 2018 Share Posted January 21, 2018 (edited) 1 hour ago, Jude1234 said: differences between immerson and Sunamp Does depend what you mean by an immersion. Assuming that you mean a traditional hot water cylinder, then you can think of it as just a large kettle. You put cold water in, heat it up with a 3 kW element at the bottom (or midpoint/top depending on design), once the water is hot enough, you use it. Then it gets refilled with cold water (does this without you knowing as it is just replacing the hot water that you need) and either automatically turns the heating element on, or waits until the timer says it is time to switch on and heats the water if it needs it (think Economy 7 after midnight). There are generally two ways to 'manage' domestic hot water (DHW) in a cylinder. One it to use the water that is actually in the cylinder, the other is to have a heat exchanger that separates the cold mains water that you want to heat up from a volume of static stored water in the cylinder. The heat exchanger does not have to be very fancy, often just a coil of pipe within the cylinder. The Sunamp is basically a box of 'heat' that cold water is passed though to get warmed up via a heat exchanger. The difference between a normal cylinder is that the substance holding the heat (heat is the old word for energy) is not water but a phase change material (PCM). PCMs are sometimes a little hard to understand, but the easy one is water changing from solid ice to liquid water at 0°C. So imaging that you have some ice at exactly 0°C, as it changes into liquid water, the temperature stays at exactly 0°C. As it changes state (called phase in grown up science) it releases energy. We call this melting (or latent heat of fusion for lab coat wearing grown ups). The energy released can be transferred, via a heat exchanger, to 'something else', usually the air around the ice. The really odd thing is that a disproportionate amount of energy is released as materials change state. So imaging that solid ice can store 2.1 kJ/kg.K (J, joule, is the unit of energy) and liquid water can store 4.2 kJ/kg.K of energy you may think that as it fuses it would be somewhere between the 2, well it isn't. It is 334 kJ/kg, or about 100 times the difference (note that there is no K (kelvin) as the temperature stays the same at 0) The Sunamp does a similar trick but at a higher temperature, about the temperature you want your hot water at (that was lucky or it would be useless). So, when you want some hot water, though some sciency magic and trickery, the material in the Sunamp changes state and releases energy though the heat exchanger, warming up the water. If you want to know exact details, ask Sunamp or a Physicist, or at a push a Chemist (not Boots or Lloyds). This allows the Sunamp to store a relatively high amount of energy is a small box. There are some other odd things that happen with PCMs, one is the ability to store a lot of energy at a low temperature i.e. room temperature, but still release the energy at a higher temperature when needed. This reduces the need to have lots of insulation around the store. To give you an idea of how high thermal losses can be with a traditional hot water cylinder, I was loosing more energy from mine than I actually needed to bathe every day (reduced it with extra insulation, so not insurmountable). Some things just need lots of insulation, a DHW cylinder is one of them. A Sunamp is not much good in an airing cupboard as it looses little thermal energy to the air around it. So pros and cons. A normal water cylinder is well understood by most people, is simple (if electrically heated) and relatively cheap to install. The downside is that they are large, can be noisy (if you have a bad installation), heavy when full of water and can have very high thermal losses. A Sunamp is much smaller and lighter and has much lower losses. It is more complicated as there is a pump and control systems, and can seem, in isolation, more expensive, but that is down to installation and location to a certain extent. I do not have any connection with Sunamp, but have seen @JSHarris installation and was quite impressed with the unit (apart from the old bleed valve position which I think is now improved). There is probably a lot more to discus about the two different technologies, and I may not have got everything correct, or may have got muddles. But basically they are both ways to make cold water into hot water, which is very basic technology and engineering, so don't fret too much when comparing systems/installations. Edited January 21, 2018 by SteamyTea 1 2 Link to comment Share on other sites More sharing options...
Guest Alphonsox Posted January 21, 2018 Share Posted January 21, 2018 Another view ! At a very high level they are pretty much the same - A cold water input, a hot water output and a 240V electrical input to provide energy. The energy is stored by some means inside to provide hot water later in the day. The difference is:- Once the energy is inside the SunAmp it tends to stay there. They are no good at providing residual heat for an airing cupboard/hot press but they wont overheat the surrounding rooms in summer either The volume of box required is a lot smaller for the SunAmp. If you're short of space this may be a good solution for you. (They are about the size of a large PC case The SunAmp stuff seems pretty much indestructible (AndyT quoted 30K cycles when I asked last week) Your plumber will look at you strangely if you choose SunAmps and claim them to be the work of the devil. I put in a couple of SunAmps a year or so ago and have been very happy. I had cause to call their technical support last October (My problem not theirs as it turned out) and they were extremely helpful. Highly recommended. Link to comment Share on other sites More sharing options...
ragg987 Posted January 21, 2018 Share Posted January 21, 2018 5 hours ago, Jude1234 said: Wow that is a decent return. If we had them would plan to have them integrated for aesthetics as well as the saving on roof tiles. How much approximately is a 4kwp PV panel and the immersun? How do you use 97% of what is generated? Is somebody at home during the day to use the electricity? Our in roof system, fitted and registered, cost £6k. This was about 2 years ago, prices have dropped since. 97% is the annual average. Our background load takes care of a bit, we try and run washers in the daytime, I time the ASHP to heat water in the daytime, in summer when we generate more I switch the ASHP off. And finally, the immersun diverts any excess to our 300l DHW. The bulk of the 3% we export is on long summer days when we have a tank full of hot water and nothing to soak up the excess. Link to comment Share on other sites More sharing options...
ragg987 Posted January 21, 2018 Share Posted January 21, 2018 Some people advocate splitting your panels East and West to lengthen the time you have solar energy. Whilst true, your annual output will drop quite a lot. If memory serves something like 20%. So if, like us, you can use most of what you generate then go south facing. Link to comment Share on other sites More sharing options...
richi Posted January 21, 2018 Share Posted January 21, 2018 Here's an off-the-wall question: What if I installed a non-MCS system, didn't try to use everything I generate, and I have an old-skool, spinning-disc electricity meter? Presumably the meter goes backwards, but how do the electricity companies feel about it? Link to comment Share on other sites More sharing options...
SteamyTea Posted January 21, 2018 Share Posted January 21, 2018 (edited) 1 minute ago, richi said: but how do the electricity companies feel about it? They are pretty relaxed about it. They eventually take you to court for theft. They don't often lose. So how would you feel about it? Edited January 21, 2018 by SteamyTea Link to comment Share on other sites More sharing options...
AliG Posted January 21, 2018 Share Posted January 21, 2018 I had a 4kW system in Scotland and generated just over 3000kWH a year. If you assume that half of this reduces your electricity bill at 13p per kWH then that is £195 of electricity p.a. You then get 3.93px3000 for the FIT payment = £118 And 5.03p x 3000 x 50% deemed export payment = £75 So £388 for a MCS system. On our new place we are paying £6500 for a 5kW system with black panels and a immersion diverter (forgotten the brand at the moment), priced over 12 months ago. You can probably get a 4kW system from a MCS installer for £5000ish today. £388 on a £5000 is a pretty good return today especially as it is index linked. Payback period is not the correct way to look at it unless you plan to sell the house soon. I did consider east/west facing as suggested on the new house, but my conclusion was that south facing panels will generate power much longer than east west facing panels. They will generate over more of the day but at a lower rate. A Sunamp type device to store the electricity is a better idea. Even if a Sunamp allows you to store all the electricity you use, you cannot run your numbers on 13p per kWH for electricity as no one would ever use an immersion heater to heat their hot water. The equivalent cost is an ASHP or gas boiler which is more like 3.5p per kWH for water heating. Having an ASHP is probably one of the best ways to increase the usage of electricity on a PV array. Link to comment Share on other sites More sharing options...
Jude1234 Posted January 21, 2018 Author Share Posted January 21, 2018 Wow there is so much knowledge on this forum. Thank you so much everyone for taking the time to explain it to me. Definitely food for thought Link to comment Share on other sites More sharing options...
Declan52 Posted January 21, 2018 Share Posted January 21, 2018 39 minutes ago, richi said: Here's an off-the-wall question: What if I installed a non-MCS system, didn't try to use everything I generate, and I have an old-skool, spinning-disc electricity meter? Presumably the meter goes backwards, but how do the electricity companies feel about it? Pot noodle lids and magnets stop it spinning as well!!! Link to comment Share on other sites More sharing options...
dpmiller Posted January 21, 2018 Share Posted January 21, 2018 /allegedly. 1 Link to comment Share on other sites More sharing options...
ProDave Posted January 21, 2018 Share Posted January 21, 2018 1 hour ago, AliG said: I had a 4kW system in Scotland and generated just over 3000kWH a year. If you assume that half of this reduces your electricity bill at 13p per kWH then that is £195 of electricity p.a. You then get 3.93px3000 for the FIT payment = £118 And 5.03p x 3000 x 50% deemed export payment = £75 So £388 for a MCS system. On our new place we are paying £6500 for a 5kW system with black panels and a immersion diverter (forgotten the brand at the moment), priced over 12 months ago. You can probably get a 4kW system from a MCS installer for £5000ish today. In other words the total FIT payment is about £193 If it costs £2K more to get a system installed by an MCS contractor so you can claim the FIT than it does for a DIY system and no FIT then it will take just over 10 years to recover the "MCS premium" That's what I am battling with. In my book the payback time for the mcs premium needs to be no more than 5 years or I will be going the DIY and no FIT route. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 22, 2018 Share Posted January 22, 2018 (edited) I am not sure that the MCS premium is anything like £2000. If the installer can get modules at 50p/W, then that is a couple of grand for a 4 kWp system. 2 guys to install going to be £200, electrician about the same, so £400 Rail and fittings probably about £300 Inverter about £1000 Scaffold maybe £300 if easy, £700 if hard, let us say another £400 Office costs around £200. So we are up to £4300 There may be some sales commission that needs to be added on and I have not added any profit for the company yet. But let us say that the cost of install a system is around £5000 to £5500. There is not going to be another £2000 added to that, the market would not stand it (actually it might once I saw some data). I suspect that companies that are installing PV these days are just paying the MCS registration charge out of normal profit and not charging a premium. I seem to remember that the fee was not that high (a few hundred quid). If that is the case, short of fitting yourself by ignoring most normal rules for health and safety, or you already have everything in place because it is a new build, I don't think that it is worth not getting an MCS system and claiming FiTs. I think it is way too easy to find 4 kWp of modules on eBay for a very low price and assume that a registered installer is paying no more. The very cheap modules are probably from a bankrupt company, so they distort the market. I found these at 40p/W https://www.cclcomponents.com/trina-solar-275w-honey-polycrystalline-solar-module-60-cell-silver-frame?gclid=EAIaIQobChMIz5ak6YLr2AIVTbftCh2_xgTrEAQYAyABEgJdIvD_BwE But that would only reduce my fag packet estimate by £500. A quick look at the government data (I like data, takes the guess work out) https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/616027/Cost_data_summary_2016_17.xlsx Show that in 2016/2017 the mean price was £1866/kW installed for up to 4 kW2 systems. So around £7500. There is quite a variation £1749 if installed in January, £1977 if installed in April. Choose your installation date carefully. There is less of a variation between the upper and the lower prices, around £36/kWp on average, but goes to £41 in December, January and February. Now those prices are not from all the MCS installation and are just prices reported. Most, I suspect, will be retrofits, so more expensive, and a lot will be sold to greedy people that want to convert low returns on cash savings to a slightly better return (spending an extra £7500 on a hybrid car would give a better return). So while the prices are probably near enough right, they are not representative for people like us that take a detailed interest. Edited January 22, 2018 by SteamyTea Link to comment Share on other sites More sharing options...
ProDave Posted January 22, 2018 Share Posted January 22, 2018 54 minutes ago, SteamyTea said: I am not sure that the MCS premium is anything like £2000. If the installer can get modules at 50p/W, then that is a couple of grand for a 4 kWp system. 2 guys to install going to be £200, electrician about the same, so £400 Rail and fittings probably about £300 Inverter about £1000 Scaffold maybe £300 if easy, £700 if hard, let us say another £400 Office costs around £200. So we are up to £4300 I have seen DIY kits including pane;s and inverters for £2K so my £2K mcs pewmium is about right. Remember mine will be ground mount but in any case I have my own scaffold so that is not an issue. When the time comes (which will be near the end of our build so a while off yet) I will look again and compare the options. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 22, 2018 Share Posted January 22, 2018 Those DIY kits are probably not available all the time though as they will be bankrupt stock. The only way to find out for sure is to call the people up and ask what the price is delivered to your door. I will admit that the price of PV from the government data was higher than I thought We were selling installations at that price 5 years ago (probably because the company did not pay suppliers, staff, failed to correct faults, was run by an idiot...). When I was involved with PV, the largest single, non hardware, expense was the sales commission, often about £800. I doubt if anyone gets that sort of cash these days. I never remember the MCS costs being an issue. The fact that I cannot remember what they are means they were never an issue. No one ever mentioned that we can sell at a premium because we had MCS, probably because everyone had MCS. It was possible to win or lose a sale on a fiver back then (just as the rate changed from 41 to 22p). The company of thieves I worked for (I left for ethical reasons) would usually 'throw in' an extended inverter warrantee and some data logging, but never actually deliver it. Link to comment Share on other sites More sharing options...
AliG Posted January 22, 2018 Share Posted January 22, 2018 I think the confusion here is calling the cost of professional installation "the MCS premium". I doubt a non MCS professional installation would be much cheaper. The £2000 saving is mainly due to going DIY not avoiding MCS. Link to comment Share on other sites More sharing options...
ProDave Posted January 22, 2018 Share Posted January 22, 2018 2 hours ago, AliG said: I think the confusion here is calling the cost of professional installation "the MCS premium". I doubt a non MCS professional installation would be much cheaper. The £2000 saving is mainly due to going DIY not avoiding MCS. Perfectly true. But to someone like myself perfectly capable of a DIY install, it "hurts" that I can't install approved kit myself and claim the FIT. So to all practical purposes for me, the cost of a professional install is the premium I have to pay in order to claim the FIT . My last install took me two part days. Had it not been winter with the short days it could have been done in 1. So lets say there are 2 man days to install my proposed ground mount system. Now show me an MCS registerd company that will install it for £400 Link to comment Share on other sites More sharing options...
SteamyTea Posted January 22, 2018 Share Posted January 22, 2018 15 minutes ago, ProDave said: it "hurts" that I can't install approved kit myself and claim the FIT. Get intouch with the MCS and see what it costs to be registered. Only a phone call away. Link to comment Share on other sites More sharing options...
ragg987 Posted January 22, 2018 Share Posted January 22, 2018 @ProDave, if we accept that the MCS premium vs a DIY install is £2,000, then this premium has a payback of about 7 to 8 years based on a south-facing 4kWp installation. From that point you are making £280 per year. (Numbers not adjusted for inflation or cost of capital.) Plus it frees the stressed and busy self-builder 2 mandays to get on with more value-add activities. Half-full. IMHO. Link to comment Share on other sites More sharing options...
AndyT Posted January 22, 2018 Share Posted January 22, 2018 On 1/20/2018 at 22:28, SteamyTea said: I think that @AndyT is saying that you use the immersion heater when the PV is only producing a small amount of excess energy, when the PV produces more it disconnects the immersion and helps run the heat pump. But you can only use either the immersion or the heat pump, not both. This is because there is a secondary electrical element in the heat pump and it may overload the eddy box of tricks, or kill the CoP as the stored energy is at a too higher temperature to get a decent CoP from the heat pump, which would cause the heat pumps internal immersion to kick in. Ideally you never want to use the heat pumps internal immersion heater. If you are using a thermal store then the water that you use (what comes out the tap) and the stored energy (which may be a brick, PCM or a fluid) can be separated with a heat exchanger. This gets rid of the Legionella problem (not that it is a real problem anyway, but that is another debate). For clarity, eddi looks at a threshold - it's an ITTT automation - so if <xkW use immersion or if >xkW use heat pump (not both) Link to comment Share on other sites More sharing options...
SteamyTea Posted January 22, 2018 Share Posted January 22, 2018 (edited) 1 hour ago, AndyT said: For clarity, So you can set the diversion depending on what you think best i.e. 1 kW to immersion OR 500 W to ASHP, if you want. (I hope the rest of the stuff I wrote was partially correct) Edited January 22, 2018 by SteamyTea Link to comment Share on other sites More sharing options...
AndyT Posted January 23, 2018 Share Posted January 23, 2018 Yes you can set the threshold and once that is exceeded, the relay board will swap the diversion of excess generation from device one to device two. Its a typical ITTT operation. if the threshold = <1 then divert to device 1. continue to monitor the threshold. if the threshold = >1 then divert to device 2. continue to monitor the threshold. if the threshold = <1 then switch back to device 1. 1 Link to comment Share on other sites More sharing options...
Alexphd1 Posted January 27, 2018 Share Posted January 27, 2018 I was just looking over a old quote (November'17) for 8kw in roof pv from a small local company. The break down cost for design (Inc independent roof survey), mcs paperwork and labour (2 guys for 5 days) was £2200. Link to comment Share on other sites More sharing options...
Jude1234 Posted January 28, 2018 Author Share Posted January 28, 2018 16 hours ago, Alexphd1 said: I was just looking over a old quote (November'17) for 8kw in roof pv from a small local company. The break down cost for design (Inc independent roof survey), mcs paperwork and labour (2 guys for 5 days) was £2200. That sounds pretty reasonable to me. Is that unusually cheap? Link to comment Share on other sites More sharing options...
ProDave Posted January 28, 2018 Share Posted January 28, 2018 1 minute ago, Jude1234 said: That sounds pretty reasonable to me. Is that unusually cheap? Reasonable yes for 10 man days, but avoidable for a DIY install, so still a premium you have to pay to get the FIT Link to comment Share on other sites More sharing options...
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