adrian82 Posted February 3 Share Posted February 3 Hi all, first post on Buildhub, really excited. I kindly need your advices in the below topic. I am struggling more than one winter to optimize the energy consumption for my home, in Romania and the company which installed my air heat pump setup do not have any solution for me. And I am hoping that maybe other ideas, could find a solution/advice for me. Long story short, my configuration is the folowing: air heat pump (12kW) , 1 buffer tank of 100 liters and 1 boiler tank 200 liters, connected to the heat pump, as DHW. On top, I have installed 10KW of photovoltaic panels, to sustain the heat pump. My house has 150sqm, 75 sqm ground floor and 75, at 1st floor. Have to mention, that heating is done with water pipes under the wooden floor. My question is what can I do to reduce my energy consumption during the night. Because, during the day, it is pretty much clear.I can stay only on PVs, and also to feed something into the grid as well, as surplus. Curently I consume during winter, around 25KW per night with the heat pump, only for floor heating.I also do not have any thermostats moounted. Should I mount a much higher buffer tank capacity? Meaning 400 or 500 liters? Also curently the temperature in the buffer tank is around 30 degrees Celsius, and I am not sure, whether it is not better to rise it much higher during the day, in order to sustain the floor heating during the night. I mean to act like a heat storage for night usage. Regarding insulation, my house is newly build, insulated with 10cm of Mineral Wool. The company that built my heating solution, says that I cannot do something more efficient. and i really doubt that. Of course, energy storage batteries, I do not find them feasable, due to the high cost. Thank you in adavnce, Adrian Link to comment Share on other sites More sharing options...
JohnMo Posted February 3 Share Posted February 3 Hi, do you have concrete in the floor, or is it just wood above the heating pipes? Link to comment Share on other sites More sharing options...
adrian82 Posted February 3 Author Share Posted February 3 (edited) after the pipes there is concrete , around 6-7 cm thickness and above this is glued the wooden floor, which is special designed for this type of floor heating. Edited February 3 by adrian82 Link to comment Share on other sites More sharing options...
JohnMo Posted February 3 Share Posted February 3 Have you tried batch charging the floor. Run heat at a higher temperature so it buffers heat in to the floor and then releases like a storage heater when you switch off the heat pump. You can do this the following way On 01/02/2024 at 10:03, Bramco said: @JamesPa Flow out is about 30C and back is around 25C. The ASHP is set to 35C but even when it's not defrosting, it never reaches this, so it runs continuously for the full 4 hours. When it has to defrost, you can see a dip in both the ASHP output and input and the UFH feed and return. I think we'd set the ASHP setpoint to 35C to aim to get a flow temp approaching that but with the way things work, i.e. the ASHP never really reaching the setpoint, it's actually probably working optimally, in that when the ASHP doesn't have to defrost it runs continuously, so is probably getting a great COP. Sadly can't see this on the Cool Energy units - I'm considering putting one of the open energy monitor ASHP kits in so that we can see what we're really achieving but that means draining down the ASHP loop to put a heat meter in, so will have to be done in the summer. Graphs below to give you an idea of how things work - our build was almost passive house, very airtight, MVHR, insulated slab with embedded UFH loops, so we don't need much heat and when the slab is warm we don't lose heat v fast. Warm night, so a bit above normal, no defrost. Cold night with defrost. Given it was very cold, the immersion in the UFH tank we use for a boost when it's below 5C was probably also on. Link to comment Share on other sites More sharing options...
adrian82 Posted February 3 Author Share Posted February 3 I have tried somehow like you say, meaning I turned on the heat during the day, on a higher temp, like 35C, but it is really warm day time. I was thinking that maybe I can store in a bigger buffer tank, of 500L, heated water during the day, and release it by night. Link to comment Share on other sites More sharing options...
joth Posted February 3 Share Posted February 3 (edited) Fwiw we have 80mm screed throughout ground floor, a batch charge it overnight cheap rate (octopus Go) for up to 3.25 hours, about 20kWh heat production, which slowly releases from the screed over the next 12+ hours and is generally all the heating we need. Generally under 60p of electricity input a day. (161m2 passivehaus retrofit) To get maximum energy dump during the cheap rate I crank the flow rate right up (based on outside temperature too) and then back it off down to 28°C as the screed temperature approaches that temperature, to avoid cooking the bamboo flooring (I can also close off loops where the floor is overshooting temperature, but that's rarely needed now I have exact control over the flow temp). All automated with Loxone and modbus interface Edited February 3 by joth Link to comment Share on other sites More sharing options...
SteamyTea Posted February 3 Share Posted February 3 1 hour ago, adrian82 said: Curently I consume during winter, around 25KW per night with the heat pump That will be kWh, which is the energy used, kW is the power. 1 hour ago, adrian82 said: my house is newly build, insulated with 10cm of Mineral Wool. That is really your problem, you are loosing energy though your walls all the time. What is the rest of the wall buildup? Have you seen, or done your own, heat loss calculations? Also makes me wonder how much insulation is under for underfloor heating pipes. 1 hour ago, adrian82 said: also to feed something into the grid as well Can you get a PV diverter that can divert excess power that would have gone to the grid, diverted directly to a heating element in your 200 lt water cylinder. Maybe heat the cylinder up to a higher temperature. 1 hour ago, adrian82 said: I mean to act like a heat storage for night usage. You could fit some old fashioned night storage heaters that are heated directly from excess PV, call them day storage heaters. 1 hour ago, adrian82 said: My house has 150sqm, 75 sqm ground floor and 75, at 1st floor. Not a very large house, but it should not be taking anything like the energy it is by the sounds of it. Have you checked your PV production against PVGIS, just to make sure it is working as expected? You can also look at typical meteorological data there as well. Link to comment Share on other sites More sharing options...
JamesPa Posted February 3 Share Posted February 3 (edited) 2 hours ago, adrian82 said: On top, I have installed 10KW of photovoltaic panels, to sustain the heat pump. Thats is not enough to sustain the heat pump in the winter months - Its nigh on impossible in a domestic setting, unless you have a very large array, to do this. Here is the plot from PVGIS of the monthly energy from 10kWp solar panels in Romania. In December and January thats about 400kWh/month, 15kWh per day, whereas you say you use 25kWh 'per night'. Do you know have any measure of how much of the energy being produced by your solar panels is currently being returned to the grid during the heating season. Except on mild, sunny days I wouldn't have thought it was a lot if any in the peak heating months, but perhaps it would be significant in the shoulder season. But as those above have suggested, if you do actually have surplus energy (which its likely you do in the shoulder season) you need either to change your pattern of heating so that the ASHP does more work during the day, or store energy. To work out how to store it first work out how much you need to store. Then its either a battery (expensive) or a big water tank. 1l of water heated by say 10C stores about 0.01kWh, so to store 10kWh by heating about 10C you need about 1cu m (1000l) of water. If you accept a low COP of 1, you could use an immersion to do the heating, with a solar diverter, get the temp up to 80C, which brings the volume required down to say 250l for 10kWh, assuming you need water at 40C for your emitters. You need some rough numbers to work out the right solution and, as @SteamyTea says, you musn't mix up energy (kWh) with power (kW). The latter is just energy per unit time thus power * time = energy so 2.5kW for 10 hrs = 25kWh. Same as kilometers per hour (distance per unit time - like power) * time = kilometers (distance - like energy) Edited February 3 by JamesPa Link to comment Share on other sites More sharing options...
adrian82 Posted February 3 Author Share Posted February 3 Guys , thank you a lot for your suggestions, I'll start working on those, very helpful. Regarding insulation, I knew that 10cm is not much, but at that moment that was the budget...The floor pipes are mounted on a polystiren structure, which the manufacturer (Purmo) state that has also a insulation role, beside fitting the pipes. I guess that a 500-1000L buffer water tank, to heat the water during the day and release it overnight, could be the best option in my case. Or maybe some batteries, but to store 20kW sounds expensive :). Link to comment Share on other sites More sharing options...
JohnMo Posted February 3 Share Posted February 3 Perhaps cheaper to add more insulation so your overnight demand reduces Link to comment Share on other sites More sharing options...
SteamyTea Posted February 4 Share Posted February 4 11 hours ago, adrian82 said: Regarding insulation, I knew that 10cm is not much, but at that moment that was the budget Is Romania except from the https://eurocodes.jrc.ec.europa.eu/ Link to comment Share on other sites More sharing options...
JamesPa Posted February 4 Share Posted February 4 12 hours ago, adrian82 said: Guys , thank you a lot for your suggestions, I'll start working on those, very helpful. Regarding insulation, I knew that 10cm is not much, but at that moment that was the budget...The floor pipes are mounted on a polystiren structure, which the manufacturer (Purmo) state that has also a insulation role, beside fitting the pipes. I guess that a 500-1000L buffer water tank, to heat the water during the day and release it overnight, could be the best option in my case. Or maybe some batteries, but to store 20kW sounds expensive :). Water is cheaper than batteries, just much bulkier. If you have somewhere for a large, well insulated tank, it's a good option. The control will need a bit of thought though including stratification (or not). Link to comment Share on other sites More sharing options...
PhilT Posted February 4 Share Posted February 4 47 minutes ago, SteamyTea said: Is Romania except from the https://eurocodes.jrc.ec.europa.eu/ Romania have their own rules based on building type for five different climate zones and it gets extremely cold in some of them - the mountainous ones where the R value requirement is most demanding. The AVERAGE night time temp in the whole of Romania in January is -6degC, so 25kWh per night for a 150sqm house is not bad with only 10cm of insulation, but what is on either side of that insulation, wood, bricks, blocks, how thick? Link to comment Share on other sites More sharing options...
SteamyTea Posted February 4 Share Posted February 4 1 hour ago, PhilT said: Romania have their own rules based on building type for five different climate zones and it gets extremely cold in some of them Not sure if that is better or worse than ours, where the builder decided what is important. (I was in Aylesbury last week) Link to comment Share on other sites More sharing options...
PhilT Posted February 4 Share Posted February 4 27 minutes ago, SteamyTea said: (I was in Aylesbury last week) Damn I didn't see you!? The coldest average temp here in Jan was -3 when my heat pump used 38kWh in Auto mode. Previously when I used WC mode it would have been much higher. My house is a 90's build conventional brick/block cavity with around 10cm insulation, but only 130sqm so the OP's usage seems not as bad as he might think, notwithstanding useful tips being given above to improve efficiency of existing setup Link to comment Share on other sites More sharing options...
SteamyTea Posted February 4 Share Posted February 4 8 minutes ago, PhilT said: Damn I didn't see you Cause I got a different car and sneak past the prison unnoticed. Link to comment Share on other sites More sharing options...
adrian82 Posted February 6 Author Share Posted February 6 (edited) On 04/02/2024 at 11:29, PhilT said: Romania have their own rules based on building type for five different climate zones and it gets extremely cold in some of them - the mountainous ones where the R value requirement is most demanding. The AVERAGE night time temp in the whole of Romania in January is -6degC, so 25kWh per night for a 150sqm house is not bad with only 10cm of insulation, but what is on either side of that insulation, wood, bricks, blocks, how thick? Under the Mineral Wool blocks is, I am not sure how to say it in english, but the translations would be "Autoclaved cellular concrete" blocks, having 30cm thickness. The house structure is built on concrete pillars and frames and the walls are built with those aerated blocks. Edited February 6 by adrian82 Link to comment Share on other sites More sharing options...
adrian82 Posted February 6 Author Share Posted February 6 On 04/02/2024 at 11:18, JamesPa said: Water is cheaper than batteries, just much bulkier. If you have somewhere for a large, well insulated tank, it's a good option. The control will need a bit of thought though including stratification (or not). I also agree on that, bulkier water tank should be cheaper thank batteries, not that elegant though, but all those equipments are in the technical room of the house. I am trying to figure out what kind of control will need this tank, maybe a mixing water valve, in order to deliver the right temperature through the underfloor pipes. Link to comment Share on other sites More sharing options...
JamesPa Posted February 6 Share Posted February 6 4 hours ago, adrian82 said: I also agree on that, bulkier water tank should be cheaper thank batteries, not that elegant though, but all those equipments are in the technical room of the house. I am trying to figure out what kind of control will need this tank, maybe a mixing water valve, in order to deliver the right temperature through the underfloor pipes. I confess the optimum arrangement isnt obvious to me, particularly if you plan to heat the water to a high temperature. In this case you might be best treating the tank like a thermal store and varying the speed with which energy is transferred from the store to the heating water to get it at the right temperature. Some sort of heat exchanger with a variable speed pump and feedback might do the job. Others may have alternative suggestions. Batteries are simpler, and of course will also be useful in summer, but significantly more expensive. Depending on how your feed in tarrifs work they may not make financial sense. Link to comment Share on other sites More sharing options...
SteamyTea Posted February 6 Share Posted February 6 (edited) 38 minutes ago, JamesPa said: Others may have alternative suggestions. The trouble is that this is heading into 'off grid' thinking. When off grid it has to be accepted that there are times when there is just not enough stored energy, so compromises have to be done. It really does not matter what sort of storage is used, if it is empty, it is empty. One problem with water storage is that there is a minimum temperature, below which, say 30°C, it is just an efficiency loss. Chemical batteries suffer less from this, but you have had efficiency losses during charging and discharging, so may all even out. That would require a lot of real data. What may be possible, with a bit hardware and plumbing, is to preheat the air entering the ASHP, from excess stored energy. A truck radiator and fan, placed in front of the ASHP intake, fed from a thermal store that is heated when there is excess solar, would warm the intake air. It would also reduce the inefficiency of the storage by allowing the store temperature to go as low as ambient. A bit madcap maybe, but the science is sound. Edited February 6 by SteamyTea Link to comment Share on other sites More sharing options...
sharpener Posted February 6 Share Posted February 6 Am also planning a Thermal Store - though not as big as the OP's 500 to 1000 litres. It will be charged during the night at cheap rate so the CoP will not matter too much, and initially used to heat bedroom rads during the evening. I expect some experimentation before I find out how much effective heat storage there is. If it is more than adequate to warm up the bedrooms either I will extend it to serve the living room rads during the early evening or dial the temp back using weather comp to get a better CoP. For @adrian82 I would think the requirement for night-time heat is so large that it would be worth using a high storage temp and then blending it down with either a standard UFH mechanical thermostatic valve or an ?Esbe electronic mixing valve, some HPs can control them directly. Don't think a heat exchanger will help, there is no need to keep the circuits separate and it will introduce a temp drop across it. 1kWh is 861 litre degrees. So 25kWh (thermal) is 21,500 litre-degrees and a 1000 litre tank charged up to 51.5 deg will be able to give up all the heat into a UFH circuit running at 30deg. What is not clear is if the quoted 25kW (h) is electrical energy in or thermal energy out. If its electrical input then you will need 3x as much storage assuming a CoP of 3 which would be a massive great tank. But still very much cheaper than batteries. Link to comment Share on other sites More sharing options...
Roger440 Posted February 6 Share Posted February 6 I very much like the large tank idea. Ive been looking at this, as i have, effectively unimited space for solar panels, and more or less, unlimited indoor space in the barn. It much cheaper than batteries, And simpler. And no bunch of electronics to go wrong. The question then is, do you use a heatpump to heat that water? As it will be circa 3 times more efficient than immersion. Cost of solar panels at £100 a pop V the cost and complication of a heat pump. If it works well enough, then i can not bother destroying the house to try and insulate it. Idea needs proper numbers putting to it. Which is where i tend to fall down. Link to comment Share on other sites More sharing options...
SteamyTea Posted February 6 Share Posted February 6 9 minutes ago, Roger440 said: The question then is, do you use a heatpump to heat that water You may still need a battery, all be a smallish one, to get the heat pump started. Then you need some way to stop overvoltage if the PV array is too large. So quite a bit of electronics involved. It is not like wiring up a torch. Link to comment Share on other sites More sharing options...
Roger440 Posted February 6 Share Posted February 6 (edited) 16 minutes ago, SteamyTea said: You may still need a battery, all be a smallish one, to get the heat pump started. Then you need some way to stop overvoltage if the PV array is too large. So quite a bit of electronics involved. It is not like wiring up a torch. Surely the invertor will manage the voltage situation? Yes, the start current might be an issue. But i could just use the mains for that. Someone posted a load divertor device a while back. Obviously the downside of the heat pump is, i need to be generating enough to run it. Whereas with immersion, i can use any solar power available. So on dull days ill still get something. That may not be the case with a heat pump. Just musing. Needs thinking through. The driver is, that i could, if i wanted to, put up a 50kw array, im not limited for space. Only money. The oil boiler would then be retained to heat same tank in the event of a shortfall in solar energy. Still need to avoid electronics as far as is possible, as they are, inevitably, the weak point. Edited February 6 by Roger440 Link to comment Share on other sites More sharing options...
Gone West Posted February 7 Share Posted February 7 10 hours ago, Roger440 said: The driver is, that i could, if i wanted to, put up a 50kw array, im not limited for space. What do you do with all the electricity in the summer when you don't need a large tank of hot water? Link to comment Share on other sites More sharing options...
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