SteamyTea

Capacitors are generally quite good on the power density side. The size quoted would have a mass around 120 tonnes, for 10 kWh of storage. Concrete has a specific heat capacity of around 0.8 MJ/tonne.K. That is about 0.22 kWh. While electricity is useful, even if there was a minimum price increase, store a bit if thermal energy would still be better I think.

Because 7⁰C does not happen very often. Go for the larger one, less chance of frosting up.

Because they are using statistical averages. Take a simple journey in two very different cars. A small diesel and a heavy petrol. The journey takes the same time, but the small diesel uses less fuel. But we can also measure it another way, the speed variations. Say the small diesel never goes above 50 MPH, but never below 20 MPH, but the the large petrol does 70 MPH but also 0 MPH. Mean speed is the same, 35 MPH. Then we can measure how the speed us distributed, this may swing the the MPG figure in favour of one or the other vehicles i.e. lots of town driving or lots of open road driving.

Technology Energy-storing concrete could form foundations for solar-powered homes A mixture of cement and fine charcoal can become a supercapacitor that could someday charge homes or electric vehicles 31 July 2023 By Jeremy Hsu A mixture of cement and charcoal powder could enable houses to store a full day’s worth of energy in their concrete foundations. This new way of creating a supercapacitor – an alternative to batteries that can discharge energy much faster – could be incorporated into the foundations of both buildings and wind turbines. When paired with renewable energy sources, it could also someday let concrete road foundations wirelessly recharge electric vehicles as they drive along. “The materials are available for everyone all over the place, all over the world,” says Franz-Josef Ulm at the Massachusetts Institute of Technology (MIT). “Which means we don’t have the same restriction as with batteries.” Ulm and his colleagues showed how cement and carbon black – a very fine version of charcoal – can mix with water to create a hardened block containing many branching, wire-like structures filled with the carbon. When the concrete is soaked in a common electrolyte solution such as potassium chloride, the charged particles from the electrolyte settle on the carbon-wire structures to provide energy-storing potential. They then turned two thin slabs of the material just 1 centimetre wide and 1 millimetre thick into a supercapacitor by separating them with a thin insulating layer such as paper. Connecting three of these supercapacitors produced the equivalent of a 3-volt battery capable of lighting up a small LED. The researchers say that the next step might be to create 12-volt supercapacitors that can also be connected to provide more charging power for larger devices. They calculated that a concrete block equivalent to a cube 3.5 metres on each side could store 10 kilowatt-hours of energy. That is about a third of the average daily household electricity use in the US and about 1.25 times the average in the UK. The material maintained its charging and discharging capabilities beyond 10,000 cycles, which means, in theory, that it could provide energy storage for a solar-powered home for more than 27 years. One engineering complication is that traditional concrete slabs would need to be replaced by the equivalent of “concrete plywood” made with the supercapacitors, says Yury Gogotsi at Drexel University in Pennsylvania. He suggested that keeping the supercapacitor wetted with the conductive salt solution for the lifetime of the building or road would be challenging. Still, the MIT team expressed optimism about how many people worldwide could start experimenting with this relatively simple blueprint for a low-cost supercapacitor. “The fundamental aspect of this technology is it’s two historical, ancient materials that come together, that we have known for millennia”, says Admir Masic at MIT. Journal reference: PNASDOI: 10.1073/pnas.2304318120

Really

As a trivial test, I put the kettle on, and had a look at my old CC Opti display and the new EDF display. Pretty close, just rounding error I suspect. Much more interesting is that you can manually disconnect them. Shall have to look into that, will stop the music playing from the neighbours.

Thermocline boundary layer. More to do with salinity than temperature. The melting Greenland icecap is going to change that quite a bit in the coming years.

Could it have been caused by nitrates concentration increasing due to the heave rainfall recently. Farmers have a lot to answer for. Never worked for me when I had a pond.

Except for the same top of cylinder temperature you can store more energy. Stratification is a bad term to use as it implies a boundary where the temperature makes a discrete step. That is not the case in a cylinder, why I use the term gradient. There will also be a temperature gradient between the sides of the cylinder and the middle. That gradient will 'flip' between heating mode, cooling mode and usage mode.

May need a bit of ceiling strengthening

Not idea if it is right, but seems to make sense. Basically, with good insulation around the cylinder, and keeping the top of cylinder temperature as low as practicable, the losses are probably the same. Could be why there is no information on it.

I have never seen it modelled, so hard to tell. Take a cylinder with a 0.5m diameter ad a 1.2m height. Assuming a U-Value of 0.2 W.m-2.K-1 Volume will be 235 lt. Surface Area will be 2.28 m2 Base of cylinder temperature, once settled, 36°C, top of cylinder temperature 60°C. Ambient Temperature 10°C. If one assume a temperature gradient of 20K.m-1 (about what mine is), then the power losses, when vertical, will be the sum of the top end, plus the area of the diameter (hoop), then the sum of the hoops, and finally the sum of the last band and the base area. Using a course 0.1m down the cylinder, the power losses are 18W, or if the cylinder is unused for a day, 0.44 kWh. Now lets turn the cylinder horizontally. Working out the surface area is not quite so easy here as for every 0.1m loss in height, the end area and the hoop area do not scale in a linear fashion, so I sketched it up in CAD, sliced it, triangulated it, then worked out the dimensions. Accumulative errors was between 1 and 8%, so shall use 4% as the error. The cylinder power losses are now 20W, 0.49 kWh.day-1. A difference of 0.05 kWh. The above is on a static model, but there will be some turbulence. With a mean temperature of 48°C for the vertical temperature, the mean density of the water is 988.7 kg.m-3, at the top of tank temperature, the density is 5.53 kg less, 4.48 kg more at the bottom. A total of 10 kg.m-3 difference The horizontal cylinder only has a 12°C temperature difference (because I used the same temperature gradient of 20K.m-1), so the density difference is only 5.6kg.m-3. Now without getting into Reynold Numbers and tangential surface areas, a simple way to model it would be to look at the difference in stored energy and the difference in mass as energy is the ability to do work, which can be reduced to moving a mass a distance. The vertical cylinder will have 233 kg of water in it, the horizontal one 232.4 kg, so 0.6 kg less. To move 1 kg of water, 1 metre, will take 1 joules of energy. So to move 232.4 kg 1.2 metres will take 279.6 J in the vertical cylinder. There is only 0.5 metres of height in the horizontal cylinder, so 116.2 J, so the turbulence losses will be in thee order of 42% less. So I would not worry about the cylinder orientation. I am going outside to sand some wood now the glue has set.

Have you a link to it?

Yes, and everything is highly unionised, and closed on a Sunday. I play a game with my Canadian Cousins, called "Name 4 interesting Canadians? Been playing it since 1989, still not got a definitive list.

Have you ruled out a Sunamp?

I binned a load the other day. My new draws just slide out in a shelf, couple of plywood strips as guides. Works well.

You can design the condensation risk out with a bit of thought. Temperature is not power, or energy. As long as your thermal emitters have a large enough surface area, then they can deliver enough thermal energy at quite low temperature differences.

20kWh seems a little low. You seem to have a constant base load, can you reduce that?

Welcome For everything you must do, there is another rule to say you must not do it.

Can you just bypass the PIR and remember to turn the light off.

Two things have crossed my mind. If you have a long flue, around the manufacturers limit, the gas will be cooler to start with, recovering the extra (say 5% wasted energy) will be harder. May pose other problems as well. Will only work on a combi, plumbed in as an instantaneous water heater, and you really need all your pipework in a suitable place, and insulated. So probably cheaper to add an extra 50mm of loft insulation. Or fix a draught.

One of the guys at work once made an extension lead like that, shocked the boss. I got caught out like that, took ages to work out what was wrong.

Move her to Amersham Old Town, the butler can hand deliver the TV signal. This is an aerial, can see it from Bodmin, and Penzance, and Helston, and bits of Falmouth and Truro. Luckily not St Awful, it is to discourage theft of TVs there.

With only 100mm of insulation under the UFH you are going to loose a lot of energy to the ground. Can you increase the wall insulation to compensate for it? We're is the vapour control layer? What is being done to improve airtightness?

Can you post up the link.