SteamyTea

It is kWp really

I might be wrong as I do not know the finer details, so that was just generic advice really. The main thing to always remember are the laws of thermodynamics, no one ha managed to break them yet.

I used Resintite, it is pretty cheap and can be made just about as thick or thin as you like. https://www.amazon.co.uk/Resintite-Powdered-Wood-Glue-1-5/dp/9792100415 It is waterproof as well. No idea of the EPS density, was just something I had kicking about.

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).

Glad you mentioned the export rate and the index linking, people seem to forget that bit. It is odd how people still think that the FiT rate should be the old high rate of 41p, that was 6 years ago and only lasted just over a year. As you have an ASHP, having PV could work to your advantage as any power generated can be absorbed by the ASHP and/or an immersion heater, so the 50% deemed export could work to your advantage, rather than an export meter. All you have to do is make sure that your domestic hot water (DHW) is heated up either side of Noon Universal Time. That is when, on average, you will get most power. Then you fit your lifestyle around that. You could get a more complicated system with a power diverted and use anything over a fixed amount to help heat your DHW. Storage for DHW is your cheapest option to reduce exports. Also make sure you size your heat pump correctly to run at no more than 40°C. You get a much better coefficient of performance (CoP) then.

Biggest wheels possible.

Or comic sans

How easy, and costly, is it to use a PIC to send the data wirelessly. I fancy having a go with them sometime, but the learning curve may be a bit too steep for me.

I have just ordered a new RPi3 with wireless as I thought it may be down to using the original RPi1b. I am using the code written my Matt Hawkins, bme280.py. I have similar issues with the GPS module. It 'sees' it but can't get any data from it, just says it has 'no fix', which may or may no the the case. Shall give it a day or two break until I get the new 3.

??? The TV is probably churning out 400W, each person watching it 80W.

Yeah right, I can use a bedpan to save to ever getting up as well.

I could easily live with that restriction, but it is nice to be able to get up in the middle of the night and make some tea and not have to worry about whether the water is heating or not. A m2 of biomass will yield around 2 kWh/year, a m2 of PV will give about 130 kWh/year. To put that into perspective, in December, that same m2 of PV will yield over 10 kWh. Not much I grant you, but a lot better than the 'sustainable' biomass option. Eigg has a total surface area of 30.5 million m2, at 0.25% efficiency (about what plants produce) and at an annual irradiation level of 90 kWh/m2, the island could produce about 7 MWh/year of biomass energy. There is no 'sustainable' biomass plan for the island.

Dug out my BME280 sensors and fixed them up to my RPi Trouble is I am not getting a humidity reading. It would also be nice if it was easy to use the SPI bus rather than the i2c one. I have the RTC on that and one BME280. If I plug in another BME280, it gives gibberish readings for the air pressure. How easy is it to make something that can cycle though the sensors, maybe just by switching the Vcc in and out.

I slept in the rain last night (wind changed direction and had window open). So had a little think about this 'semi' off grid problem. Could you not wire the house a bit differently so that you have light, fridge, freezer, central heating pump/controls and maybe a couple of spare sockets on the island grid. It may still be possible to use more than 5 kWp, but mush harder to. I have no idea what actually happens if you do go over the 5 kWp limit. Does it blow a fuse and need someone from the DNO to fix it, or trip out and just need a reset? Or do they do the decent thing and charge £2 a unit. The rest of the house could then be on a secondary circuit, one that is only connected to your own generation and storage. That way you can use more power if it is being generated or has been stored. As the island increases its renewable generation/storage, they may give you another, higher limit, then it is just a case of transferring a few circuits to the island grid. I also think that it is worth moving away from all combustion technologies. Shame that the island is going RE electric, then some islanders fill the local area up with smoke and fumes. Rather defeats the object.

Does it do that with the TV turned off too?

Welcome First thing you need to know when going just about off grid is what your energy and power requirements are. So you need to break them down into categories i.e. Space Heating, Hot Water, Cooking, Lighting, Clothes Washing, Vacuuming, etc. Then look at the maximum power needed i.e. 100W for lighting, 3kW for water heating, 4 kW for cooking. Then the total energy required for each over a 24 hour period. Add in some contingency and you should be able to work out the storage needed. It is harder to reliably calculate the generation from wind and solar, but that is what the storage contingency is for. Or just get a generator and a relatively small battery storage system.

All I am going to say on this subject

What a good idea. I would be quite interested in making a couple of them too. One for home and one for the car. Maybe the home one should be an inside and outside one.

Welcome I like charts

Yes, and I think that I read somewhere that the control system has to be 'non propriety', whatever they mean by that.

That is only comparing one plug which we are familiar with, against another one, which we are not familiar with. what is really needed is for the world to agree on one type that has primary and secondary features built in, and is small. it is really not hard to do. But that would take cooperation and the putting aside of national prejudices. In 2013 in the UK, there were 3 domestic deaths from electrocution.

Totally moving away from storage heaters (not that I mind as I was just highlighting some change). If, for whatever reason you change something and the cost becomes prohibitive, you don't achieve your aim either. So regardless of who a product or service 'safety' or 'best practice' body is, and it probably does not matter if it is local, national, trading block or global, they have to keep the cost of implantation down. The BS1363 plug is now rather outdated as be also protect out mains voltage circuits with other devices. But there is a good reason to keep it in the UK as the cost, and in some cases there will be danger in changing outlets (a cack-handed DIYer), far outweigh any advantage. Having worked in two industries that have loads of legislation attached to them (catering, and health and leisure), it is really not hard to comply. I do wish that all legislation, and an easy to understand guide i.e. IEE17th Edition, was freely available. There would be no excuse for non compliance apart from laziness. I also think that anything that has to be administered by a local body i.e. the local council, needs to be to the same standard. It s no good having one LA saying you can do something while another cannot.

That is the way I understood it too. All pretty basic stuff really and probably no bad thing.

This one slipped by me, does anyone know what it really means. It also may account for why I got a letter offering me free storage heaters (as long as I was on benefits, which I am not). Here is a link to some 'stuff': https://www.lot20.co.uk/