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Alphonsox last won the day on November 29

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About Alphonsox

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    Politics is killing Buildhub

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  1. I have no idea what abhorrent political organisations you choose to support - that’s your business and I have not stated otherwise.
  2. The EUCJ will rule on Monday, until then feel free to keep spouting the usual UKIP tripe.
  3. Please check your facts before posting
  4. Alphonsox

    Solar Store - heat battery

    I'm not sure your insurance company would be quite as enthusiastic, although you might be able to claim a huge vat of hot palm oil was due to your love of deep fried food. (Probably only a viable defence for those of us in Ireland or Scotland )
  5. Alphonsox

    Heat pump placement
  6. Alphonsox

    Solar Store - heat battery

    Worth reposting this from Andrew Bissell of Sunamp on Ebuild in September 2015 and recovered from the wayback machine. ===================================================================================================== Phase Change Materials Phase change materials work by storing heat when they melt, and releasing it when they freeze again. Their mode of operation is simple in principle. Melting/freezing stores/releases a lot of energy. As an example, think of water as a PCM that melts at 0oC. Water ice has a specific heat capacity of 2.000 kJ/kg/K at -10oC (and density 918.9 g/L) Latent heat of fusion of water (ice to liquid) is 334 kJ/kg Liquid water has a specific heat capacity of 4.182 kJ/kg/K at 20oC Over the temperature range -10 to 20oC there is (about) 10*2.000 + 334 + 20*4.182 = 20 + 334 + 84 = 438 kJ/kg of total heat capacity. NOTE that over 76% of the stored energy in that 30 degree band is latent heat and less than 24% is specific heat. For comparison, ice would store ~60 kJ/kg over 30 degrees from -31 to -1oC; water would store ~125 kJ over 30 degrees from 1 to 31oC. (See: http://www.engineeri...ties-d_162.html http://www.engineeri...ties-d_576.html) So the effect of having a solid/liquid phase change in the temperature range of interest is to dramatically increase the heat capacity over the range. That's why we use PCMs. Of course not all materials are suitable to be PCMs. To be a PCM, a material has to have the right melting point for the application, a suitably high latent heat capacity (and ideally a high specific heat capacity too), and be safe and reliable over the long term. Choice of PCMs There are two main classes of Phase Change Materials for room temperature class applications (i.e. 10 - 90oC): Organic - paraffins, waxes, fats, oils, fatty acids, etc Inorganic - salts, salt hydrates, metals (e.g. Woods metal) It was easy to choose between these, and then hard to execute the choice. Organic materials are common and easy to get, easy to work with, have a wide range of tuneable melting points, but suffer from defects that, in my view (and Sunamp's), make them fundamentally unsuitable for use in household heat stores. The outright show-stopper for me is the high flammability of organic materials. I would not put tens or hundreds of litres of hot oil in a store in my home, and I wouldn't ask anyone else to do the same. The other key defects of organic materials are lower energy density (typically half that of salt hydrates) and poor sustainability ("bio-derived PCMs" often derive from palm oil, which is strongly linked to tropical deforestation - sustainable sourcing may be available, but how can we be sure?; paraffins are directly derived from oil refining). I don't absolutely rule out use of organic materials in future, in some capacity (perhaps in industrial heat stores, or ones buried underground), but I can't recommend their use inside homes. Of the inorganic PCMs, the metals are costly, physically very dense (I mean g/L not kWh/m3) and toxic. Pure salts generally don't melt until much higher temperatures. Salt hydrate PCMs Sunamp uses salt hydrate PCMs. We do so because they are non-flammable and have high energy density (very similar to water and water ice), and offer a range of melting points. As you know we work with families of materials (where we have applied for patents) based on: Sodium Acetate Trihydrate (primary melting point: 58oC; tuneability 46 - 58oC) Strontium Bromide Hexahydrate (primary melting point: 88oC; tuneability 75 - 88oC) Only SU58 (our 58oC PCM using Sodium Acetate Trihydrate aka SAT) is in full-scale production as yet. It is our mainstay material, used in the heat batteries (HB58) used in SunampPV and other forthcoming products. Our PCMs were developed with University of Edinburgh, and there are forthcoming academic papers due. For reasons of academic priority, I can't say everything I'd like to about the materials yet. What I can say is that conventional SAT PCM is used (as some here have observed) for hand warmers. These can be stored at room temperature and can be activated by clicking a metal disk inside. They are recharged by fully melting the SAT inside by heating the hand warmers in a pan of hot water. There is something to like in this approach - storability at room temperature - BUT there are some serious drawbacks: Conventional SAT materials used in hand warmers degrade after hundreds of cycles due to "phase segregation" - an anhydrous fraction precipitates out like a sediment; what is left behind is more dilute and less effective They need to be activated - when do you choose to do that? When the materials cool back to room temperature for storage,the specific heat is lost, so total energy storage is lower than it might be They don't reach 58oC when re-activated and the energy released is less Sunamp's SU58 is formulated differently. It contains additives that achieve two things: A polymer that eliminates the degradation effect. All the science points to the degradation being completely eliminated. Details to follow in the scientific papers, so please be patient. However what we have learnt does allow us to offer a 10 year limited warranty similar to the best electric batteries. It includes a nucleator, which means that the material starts to freeze cleanly when cooled to 58oC. This means that there is no control issue about when to activate the material, no lost energy and we achieve the full 58oC. We have evaluated many other materials, and continue to do so. The 88oC family is very exciting and essentially new. Many of the best ones at other temperatures are already in the public domain, though not always with their best formulations. Sunamp Heat Batteries A heat storage appliance like SunampPV needs to contain a heat store. In Sunamp's case we use Heat Batteries. After several generations of refinement (the first Sunamp heat batteries were deployed in field trials in 2013), we have arrived at a red plastic-cased cell, the shape of a large cereal box (115 mm wide x 463 mm long x 499 mm tall, externally occupying 26.5 dm3), weighing a little over 30 kg. A heat battery cell offers: 45 Litres of instant hot water or 2.2 kWh of thermal energy when discharged through a TMV set at 55°C, from 73°C to 45°C. Higher or lower performance may be delivered for other applications and operating conditions. For example jsharris wants hot water at 42oC. In that mode, two cells in series would deliver about 4.4 kWh before dropping below 42oC. Three cells about 6.6 kWh, provided those cells were charged to an average 73oC using, say, off-peak electricity or diverted solar PV electricity. SunampPV includes two such cells (sitting side-by-side, connected in series) and hydraulics to allow the electric charging of the cells. When discharged, cold mains water flows into the appliance and through heat exchangers in the cells. The cold water picks up heat from the PCM. Initially it transfers heat from the hot liquid PCM (which cools from 73 to 58oC progressively), and then from the PCM as it freezes (at 58oC). Finally once the PCM is all solid, the solid cools further (from 58oC downwards), continuing to transfer heat to the mains water. Is the end of useful energy when output drops below 45 or 42 or 40oC (e.g. in a hot water application replacing a hot water tank with immersion heater or an instant hot water heater), or when the output approaches cold mains temperature (e.g. when SunampPV is connected as a pre-heat to a combo boiler**)? That's for you to judge based on your application. It affects useful heat output: there is about 20% of total heat to be had from 45oC to ~11.5oC. We quote heat capacity without this at cell level, and with this heat at SunampPV level (as SunampPV is designed for use with combis, where pre-heat is useful). (For SunampPV spec sheet please see: Apologies that it needs a little updating. For example it overstates the mass by 10 kg (it has come in below estimates at 80kg +/- 1 kg) Power and Flow Rate One very critical parameter that almost all other PCM system developers tend to fudge is power. This is because the thermal conductivity of PCMs tends to be very low (<< 1 Wm-1K-1), so its hard to get the heat in and out fast. Its all very well that PCMs offer high energy densities, but if you can't get at the energy, is it useful? Sunamp Heat Batteries are designed to overcome this. A pair of heat batteries in series can sustain over 12 litres per minute of discharge when fed with cold mains water at 10oC and deliver most of the energy in a plateau at just over 50oC. Power is over 40 kW peak, 35 kW sustained, with over 30 kW still being delivered when falling to 45oC. A couple of points to note: The plateau temperature doesn't change much whether the mains cold inlet is 5, 10, 15 or 35oC. This means power scales UP in cold conditions, when mains temperatures would be say 5oC. This is desirable. There is very little water stored in the appliance - for SunampPV about 5 litres is present. This water comes out at high temperature (whatever temperature the PCM is at, whether 70+oC at the end of charging or 58oC during the freezing plateau) so there is IMMEDIATE hot water - no waiting for a heat exchanger to heat up; no initial slug of cold (except what is in pipework). (Little water in the appliance, a different slug between each discharge and high temperature storage and, at least after every charging, over 65oC, absolutely minimises legionella risk.) Frankly I wanted to stomp the power problem into the ground, and I am proud that we have. One consequence is that SunampPV outperforms most combis it could be paired with (which is what we want). Another is that SunampPV can be used as a high flow rate electric hot water heater at >30kW when connected to a 3kW spur circuit (albeit not continuously, but if the average duty cycle is 10% it works). We haven't yet tested maximum flow rate at maximum rated mains pressure. We'll update when we know. Heat Loss When building a small appliance, smaller than a water tank of equivalent heat capacity by 3 to 4 times, you risk being a mouse (i.e. having the surface area:volume ratio work against you). You also risk having total insulation volume end up close to or greater than your heat storage volume. For this reason SunampPV uses Vacuum Insulation Panel. We can do that because we have flat surfaces to insulate, and because the total surface is quite small (so we could afford to do the right thing - VIP is expensive per m2). So far preliminary heat loss testing has been performed in-house using the approach used to test an electric storage water heater, wherein there is thermal draw-off and recharge using a tapping cycle during the hours of 07:00 to 22:00. This suggests 0.7 kWh / 24 hour heat loss from SunampPV. We are about to send a unit to a test lab for confirmation and other tests, so should have better data soon. I am sorry that the 5W figure clouded this. That is the upper bound of the electrical standby load. I hope we can further significantly reduce the thermal losses later. Regulatory If you read this after 26 September 2015, either we will have ErP certification from the above-mentioned test lab OR SunampPV will temporarily be off the market until we get ErP certification. Equally SunampPV doesn't yet have CE mark (although it has passed all the related lab tests for EMC and LVD). We believe SunampPV meets the UK water regulations, but WRAS certification is still pending. SunampStack Other Sunamp products will be composed of different numbers of cells in series, parallel or series-parallel arrangements. We offer cells to OEMs and for our own products. While we are not offering bare cells direct to the general public,we expect to offer SunampStack, a configurable product line, soon. SunampStack is composed by integrating multiple layers of heat batteries Each layer is composed of 2, 3, 4, 5 or 6 cells Layers may be stacked up to 4 high (2,350 mm) High degree of flexibility and modularity to meet different storage requirements from 4 to >50kWh (90 to >1000 litres) Example SunampStack: 5 cells wide by 3 layers high = 15 cells Occupies 655 mm wide x 540 mm deep x 1800 mm high Delivering 675 litres above 45oC via a TMV set at 55oC or 33 kWh That's all for today folks. Next I'll try to tackle some of your specific requests. Please be a little patient. Andrew
  7. Alphonsox

    The Build - Mission accomplished! We're in!!

    Congratulations - looks great
  8. Alphonsox

    100% off grid?

    JSHarris pricing looks on the mark to me. Very similar to the pricing we came up with when we were looking. By the way the Kensa calculator is extremely pessimistic and doesn't have options that come close to a Passive spec house. It over-specs my requirements by a factor of 4.
  9. Alphonsox

    Sunamp container bulging

    What is the flow detectors role in this ? I has assumed it was just there to detect cold water flow during the charging cycle and hence switch charging off. Is it performing a more complex function during charging ? Looking at its position in the water loop I assume it must be.
  10. Alphonsox

    Sunamp container bulging

    I disagree - Sunamp seem to be loosing their USP in the domestic market. If they cant reliably capture excess renewable energy then they move to being just another Megaflow competitor.
  11. Alphonsox

    Sunamp container bulging

    There seems to have been a step up in efficiency between the SAPV and the UniQ units. The original versions had a ErP rating of "C" while the latter get a "A+" with very similar heat loss rates (@0.7KWh/24h). I assume the efficiency gain is a function of the new charging mechanism.
  12. The one thing we missed and that I regret not doing was putting in door mat wells at the back doors in the utility.
  13. Alphonsox

    Sunamp container bulging

    Is the changing system in the new designs fundamentally different to that in the original SAPV units ? I have a couple of the originals and assumed they would accept input at any stage of discharge.
  14. I'll accept that selecting 1 out of 5 identical beach trees might be open to interpretation, but this was a 200 year old Redwood the size of an Apollo rocket......