Marvin

Yes if you need winter heat and you have summer power this is the challenge....

True, but this will lessen the cost effectiveness.

Thanks for this. Yes this is fun but for me I need about a 4m3 storage that will last for months.

Helium. I think any sealed tank causes massive expansion risks. increases the cost, now instead of an old steel bin I have to use a pressurised tank! no this has to be cheap low risk and make a saving.

Yes but this ups the cost and complexity

what is SHC?

Hi @Iceverge Not as much space or where needed! However I calculate we have about 2000kWh available. This is at present a feasibility study. I have done studies for our home for energy from wind and rain and cannot make them sensibly work. Yes I need a pay back window and if I can't end up with a sensible one it's not going to be worth it. M

Aerogel is good but expensive with a 650C melting point (being made from the same sort of thing as sand (silica)? What is it? about £10 a square foot 10mm thick? Comparative thickness of mineral wool 40mm? this might blow the budget...

What temperature will VIPs withstand?

Could add the warm air to the MVHR inlet.

Hmm. What volume of air would you need to produce the potential of 1kWh of heat?

Hi @SteamyTea It's good to have someone capable to review my workings. I double checked because I thought you might. Present theory: 1. From centre of store to outside: Sand, steel container, mineral wool, external weather protection. 2. Electric energy, to heat air, to heat sand. Heated sand to heated air to building. Storage capacity, thermal loss over time and building requirement are the next hurdles...

Is this right? Dry sand density between 1520-1680 kg/m3 (say 1500 in the calculation below) Course sand, dry, specific heat capacity is about 800 Joules per kg per degree of temperature change. Course sand, dry, thermal conductivity 0.25 W/m K 1kWh equals 3,600,000 joules And therefore, ignoring all factoring of energy loss due to energy conversion etc(what I call "in theory"): Heating up 1kg of dry course sand would be: 450 degrees temperature change times 800 specific heat capacity times 1kg in weight, divided by the amount of joules in one kWh: 450 x 800 x 1000 / 3,600,000 = 1 kWh.

Ditto.

I @SteamyTea It obvious to me from the graph that you are running at bottom power whilst still living! Do you have a hand bell at the front door? The thermal efficiency of your property and or the inside temperature seem to be the only things where there is room for manoeuvre. Like the windows ideas! We lose about 30% of the heat out of our windows. Had thought of insulated secondary demountable covers, but would have to convince SWMBO! I would try and mould the panels to the profile of the window opening by fixing a coat of plastic to the window and reveals cutting a bit of insulation the the right hight and width and then foaming one side of it a squishing onto the plastic. God help me if I make a mess of the carpet....

Reading the original post first I would like to clarify: If the aim is a prediction for the next 3 hours I can't help. If your looking for general predictions of daily sunlight over a month I can do this. Predicting sunlight is easy on fully cloudy days and completely clear sky days otherwise good luck! The value of any information can only be decided when the purpose is confirmed. If I was anal about needing the house to respond to sunlight I would use sensors. If it was solar gain deflection I would use sensors. If it was to calculate solar gain or PV output this can be done. If you want to know exactly how long sunlight hits a particular spot on your building you can install a 12PV panel obscured to only produce enough power when lit by sunlight (or add a relay that need a minimum voltage to start the meter)and a ayron JR-HM001 Snap in Mechanical Hour Meter Rectangular Hour Meter for DC 6V to 80V and an appliance to use up the power produced. Hope this helps someone. We live on a windy island, where expected hit and miss weather days are frequently wrong. M

Hi @dnb Can I ask what the info is for. We live at the bottom of the island. If you require detailed info for calculation PV generation or solar gain I have no quick answers but have some suggestions. Marvin

Plus one for @SteamyTea's comment about stuff in the loft.

As recorded Item Low High Typical average per hour kWh used total hours kW per hour 24 hours Fridge freezer 0.050 0.506 0.1 0.130 25.64 197.50 0.130 3.116 Freezer 0.002 0.293 one or other 0.070 1.71 28.25 0.061 1.453 Both are auto defrost....

Hi @TerryE We have also been looking at energy use figures and its quite interesting comparing how homes work. Our bungalow floor area is 104m2. I monitored the outside temperature hourly using our weather station and compared the results with the local weather station which is only 1 mile away, and sure enough the temperature records were the same so now I just use their data. We measured the daily power demand for as many appliance as possible in our home and keep daily records from when the ASHP was installed. Our average over a day, lowest background power use, is about 300W continual We have east and west facing windows and this gives major solar gain - even during winter on bright days. Our total energy purchased in a year will be about 3400kWh and PV production about 6600kWh so 10k potential. The ASHP uses about 1840kWh a year. The car uses about 640kWh a year These we measured: The MVHR uses about 262kWh a year The fridge freezer uses about 120W an hour or about 1000kWh a year The freezer uses about 550kWh a year. The sky box uses about 280kWh a year The router uses about 130kWh a year. So minimum energy used 2,200kWh a year! Here's a useful link for those who wondered what household item uses what power: https://www.electricalsafetyfirst.org.uk/guidance/safety-around-the-home/home-appliances-ratings/?gclid=CjwKCAiA2L-dBhACEiwAu8Q9YGohisCTL8TQ-HJ_pPVFchK3PdnWzEwFaSzpcjK6f0lcE7iBMI3GPhoCOxIQAvD_BwE Also the more cooking and laundry done in a day the less heating seems to be required! During the winter the the daily non heating use increases but not between 10pm and 8 am so this has to do with equipment use. I noted that the fridge/freezer uses less energy during the winter! Marvin

Sadly no room for more PV unless I use the north facing roof but our RWH runs on 12 volt system with 2 panels on the shed.

I would not use foam. I have used mineral wool. Without fluffy, when the bath is full of hot water, the air underneath warms up, so I believe it keeps the bath warmer longer. That and making sure the space under the bath is airtight. M

Homework! Installing battery backup.

Hi @Question The first thing I would look at is the chimney stacks. Its very difficult to decide such a thing. 30 years is a long time. I know that we didn't like the idea of replacing it in 10 years time. However we planned to install PV panels on the roof so didn't want to do it after that. We had the same decision when we bought our bungalow. I looked at the other properties around and noticed problems with mortar coming out of ridge tiles joints etc, and the roofing felt in ours was not so good especially over the soffit so we ended up replacing the lot. I felt happier using dry verge and dry ridge systems which avoided relying on mortar. But as @ToughButterCup says a proper independent inspection is best.

It also depends on the quality of the materials and installation to start with.