SteamyTea

Plants are meant to do this, but when I did an experiment on it, the variation was tiny as the grass grew. There are paints that change colour with temperature. In practice, as radiation is proportional to the cube of the absolute temperature difference, the only times that a meaningful difference happens is during summer, so a reflective coating is all you need, in winter the differences are too small most of the time (maybe 10 days in the UK). City in Sierra Leone covers buildings in mirrors to fight extreme heat People in Freetown, Sierra Leone, are increasingly exposed to extreme heat due to climate change and the urban heat island effect, but covering homes in a reflective film significantly cut indoor temperatures By James Dinneen 3 June 2023 Reflective film installed on the roofs of two buildings in Freetown, Sierra Leone MEER Tens of thousands of people in Freetown, Sierra Leone, live in informal settlements dense with metal and concrete buildings that trap heat and make heatwaves more dangerous. An experiment has shown that covering such buildings with a cheap mirrored film can substantially reduce the temperature inside. Since becoming the chief heat officer of Freetown in Sierra Leone, Eugenia Kargbo has experimented with all kinds of ways to protect the city from heat. When a group of researchers approached her with a plan to cover the city’s buildings in mirrors to cool them off, she thought it was worth a try. “I said, ‘why not?’” The proposal came from a US non-profit called MEER, an acronym for Mirrors for Earth’s Energy Rebalancing. Founder Ye Tao was in search of a place to test the cooling effects of a reflective film the organisation had developed out of recycled PET plastic and aluminium. In theory, a building covered in the film would absorb less of the sun’s radiation and be cooler than one roofed with metal or tar. Tao had heard about Kargbo’s efforts to mitigate heat in Freetown, which have included planting hundreds of thousands of trees across the city and installing shading structures made of reflective plastic in a crowded marketplace. So, he asked her about testing the film. Temperatures in Freetown regularly spike above 40°C (104°F) during the dry season from December to April, and remain hot even at night. The hottest days are projected to become more frequent with climate change. Sign up to our Fix the Planet newsletter Get a dose of climate optimism delivered straight to your inbox every month. Sign up to newsletter The heat is also exacerbated by the urban heat island effect – a phenomenon in which urban areas get hotter than nearby rural areas due to less vegetation, less air flow and more heat-absorbing material on buildings and roads. Kargbo was interested in anything that might provide cooling effects indoors. The city’s buildings are hot and getting hotter. “The heat data shows everywhere in Freetown is getting hotter, but there are also communities that stay hotter throughout the day,” says Kargbo. This was particularly true of the numerous informal settlements built along the coast and the deforested hills around the city. Most buildings in the impoverished settlements are made from uninsulated concrete walls and corrugated zinc roofing that absorb and trap heat. Kargbo says the heat and humidity, along with high levels of air pollution in the settlements, make for a “toxic combination” for residents’ health and well-being. In consultation with residents, Kargbo and other city officials along with Tao and his colleagues decided to test their reflective film in a settlement called Kroo Bay. The settlement is one of Freetown’s largest with more than 10,000 people living in roughly 1 square kilometre. Read more: El Niño climate events cost tropical countries trillions of dollars Jalahan Sesay, a recent graduate from the University of Sierra Leone who surveyed residents as part of the MEER project, says most people in Kroo Bay sleep outside during the hottest time of year, because staying indoors is intolerable. Most buildings lack a ceiling to separate the living space from the roof. “It’s like having a radiator on top of people’s heads,” says Tao. Working with local carpenters, Tao and his team installed mirrored film on the roofs of two residences. To compare its effectiveness against other cooling strategies, they also painted the roof of one residence white and added a new metal roof to another. All four buildings were similarly constructed and had around 180 square metres of roof area. During the day, the interior temperature of the building with the new zinc roof was on average 1 to 2°C cooler than before, and the building with white paint was around 3°C cooler. Inside the two buildings covered in film, it was 6°C cooler, says Tao. The temperature of the roof on the two mirrored buildings was 15°C cooler than without the film, on average. A heat map (left) shows the temperatures of the four roofs (pictured right), with darker areas signifying lower temperatures. While the new metal roof (bottom left) appears coolest, temperature measurements revealed the two roofs covered in reflective film (right) were actually cooler. MEER Sedie Sowa, another MEER intern who surveyed residents in Kroo Bay, says families who live in the mirrored buildings are pleased with it. “They say they sleep comfortably,” he says. David Sailor at Arizona State University says assessing the amount of cooling depends a lot on measurement conditions – cooling effects from reflecting sunlight will be greatest during days with the most solar radiation, for instance. But he says a 6°C reduction is substantial. “There’s a lot of potential there not just to improve comfort, but to save lives.” Tests are ongoing, but Kargbo says she is encouraged by the results, and aims to roof many more buildings in Freetown with reflective film. If an entire neighbourhood or more were to be covered, Tao says the cooling effects could accumulate as air flows across roofs, lowering air temperature across whole areas and not just within individual buildings. Infrared-reflecting paint can cool buildings even when it is black By Layal Liverpool 24 April 2020 A new paint reflects infrared with a layer of polymer, which helps keep objects cool Jyotirmoy Mandal A two-layered paint that reflects infrared light while maintaining its colour could help keep buildings and vehicles cool under hot sun. This could help reduce energy used in cooling, such as by air conditioners. This coating was developed by Yuan Yang at Columbia University in New York and his colleagues. It consists of a top layer of commercial paint, which provides the colour, and a bottom layer made of a polymer similar to Teflon, which reflects infrared light. Sunlight contains both visible and infrared light but the infrared accounts for the majority of the solar energy, says Yang. When the sun shines on an object coated with this paint, the top layer absorbs certain wavelengths of light, depending on the paint’s colour, while the bottom layer reflects infrared light, preventing the object from heating up. A similar cooling effect can be achieved using white paint or metal mirrors, but Yang says the advantage of this new paint is that it can be any colour desired. Read more:Earthquake-resistant paint could help brick buildings survive tremors Usually black paint absorbs heat, but painting an object with a black version of this new coating kept it about 16°C cooler than when an object painted with commercial black paint was exposed to the same amount of sunlight. In another test, the new paint coating was found to be able to maintain its colour despite being placed in an oven at 60°C for 30 days. Yang says this paint could help save electricity and reduce carbon dioxide emissions. “Solar reflective and thermally emissive surfaces offer a sustainable way to cool objects under sunlight,” says Mingqing Wang at University College London, who was not involved with the work. This could be useful in tropical locations to help keep buildings cool and reduce electricity consumption from air conditioning, as well as to prevent cars, buses and trains from getting too hot, she says. An intriguing next step would be to try and add more functionality to the coating, for instance to enable the energy from the reflected infrared light to be harvested to generate electricity, says Wang. Science Advances DOI: 10.1126/sciadv.aaz5413 Superwhite paint can cool buildings even in hot sunlight By Adam Vaughan 21 October 2020 Some buildings are already painted white to help with cooling Johner RF/Getty Images A new superwhite paint is so reflective that it can cool a surface to below the surrounding air temperature, even under sunlight. It could help reduce the use of energy-intensive air conditioning in hot countries. With global energy use expected to grow 90 per cent by 2050, ways to passively keep cool without using energy will be vital in coming decades. While “cool roofs” painted white are a common sight in hot climates, materials experts think they can do one better. Xiulin Ruan at Purdue University and his colleagues developed a white paint that was so reflective and good at radiating heat that it cooled a surface to 1.7°C below the surrounding noon air temperature during tests in Indiana. Compared with existing, commercial heat-reflective paints that reflect about 80-90 per cent of solar energy, the new one managed 95.5 per cent. Although it sounds counter-intuitive, the surface can be cooled below the surrounding temperature because it emits enough heat through radiative sky cooling, the natural process of a body under the sky – such as a roof – radiating heat out to space. Light-coloured surfaces regularly do this on cloudless nights, but it wasn’t until 2014 that we found a material that managed the feat in daylight, when our cooling needs are greatest. Read more:Infrared-reflecting paint can cool buildings even when it is black Compared with that breakthrough, Ruan says his team’s paint is thinner, cheaper and could be easily scaled up. The acrylic paint is made with calcium carbonate, and partly achieves its qualities by containing particles of many different sizes, which help to scatter different wavelengths in the solar spectrum. Ruan estimates a typical US home of 200 square metres would save about $50 per month on cooling costs, compared with using an existing heat-resistant paint. “This is a very nice result,” says Aaswath Raman at the University of California, Los Angeles. “It demonstrates a paintable solution that employs materials commonly used by the paint industry, and gets reasonably good cooling performance. One potential limitation could be its use of organic solvents, but that could be addressed in the future.” Cell Reports Physical Science DOI: 10.1016/j.xcrp.2020.100221

Have a look here and see what size trays they have. https://www.gseintegration.com/en/solutions/gse-in-roof-system/ Or Midsummer. https://midsummerwholesale.co.uk/

Especially true as the writing is on the wall for combustion technologies, in all sectors, including pub gardens.

No. It is probably just crushing the solid part, or at least making a more uniform matrix. The solid material will still be there, just with less air mixed in with it. This is why on a roll of mineral wool type insulation, it specifies the thickness. Crushing in more material reduces the k-value. You can think of it as a stud, in a stud in a wall, reduce the depth of them and you not only shorten there thermal path, but you also reduce the air thickness, reducing the performance even more.

Just work it out from first principles. The solid material will have a k-value, and that will stay they same, just shorter in length. The air, which is what actually does the majority of the work, will be reduced in mass/volume, and will also be shorter in length. So as long as you know the original densities, you can calculate the volumes, and therefore the length at the correct compaction level. Then recalculate for greater compaction.

No, I think in 20 years my power has been off 3 times, only once for over half an hour. And I live in a very windy place.

I think the problem is disposal of them, rather than the normal usage of existing ones. They cannot be burned easily and they cannot be buried (no point, they don't degrade).

Spoonerism is just swapping the first sounds of each word: what makes me such a shining wit. Malapropism is using the wrong word, usually to comic effect, so I may just fade into Bolivian.

They will be close the the mean air temperature, which is about 18K lower than body temperature. The problem is that tiles conduct heat well, so they may feel cold. Will also help water evaporate away quickly, though this can cause discolouration of the grout (ask other about the best stain resistance grout).

Boil the fruit with lots of sugar and call it jam. For some reason, we are being inundated with flies this autumn. While I like the idea of a green roof, not sure I want to attract critters close to my bedroom window.

If it was on the ground, it would be called scrubland. Though they do say that a weed is only a plant in the place you don't want it.

Sounds to me like the only thing missing is a generation meter. Being France, there will be several metres of forms to fill in, after lunch, and then weeks of waiting until a civil servant stamps it.

You can get a water cylinder with a heat pump built in, that may be the cheapest to run, though the most expensive to buy (the Ecocent is just a branded Chinesium model at 4 times the price). While an E7 DHW system is cheap to run and install, it does mean that your daytime electricity is expensive, that will negate much of the savings if the A2A heating. Instantaneous water heaters are good, but need to be high power i.e. 10 kW or more. This may mean updating the consumer unit. You may need a water softener as well. So really just a case of booting up Excel and working it all out.

May be micro inverters on the back of the modules.

You can get PV diverters. These units are designed to turn on a remote load i.e. water heater, when they sense power being exported. There is usually a minimum generation they can work down to, so good for resistance loads, not so good for inductive loads like a heat pump. Heat pumps don't like being started and stopped too often. The usual way to 'run' a heat pump from PV is ti take the statistical route i.e. max generation is around local noon, so a couple of hours either side. You will still be importing energy during these times, but less than usual. You have to balance that with whatever you get changed for you importing energy, it may still work out cheaper to run the heavy loads at night, only you know your tarrif. Depending on what you get paid to export, you may find that the cash generated is a better option.

Or a water pipe with clear ends.

Can you run a Mac OS on it?

Did I get it the wrong way around, they are fixed current devices (I think LEDs are the same).

I am not sure about this (as not an electrical engineer) but I think that PV modules are fixed voltage, it is the current that varies with solar intensity. If that is the case, then as long as the module voltages match, there should not be a problem. If that is not right, then maybe individual module optimisers can overcome the mismatch.

3 metres

Feel free to improve the code and post it up.

"The build starts with lovely weather but by the Thursday most of the UK has a yellow weather warning for rain, we had 23mm of rain Thursday, 14.2mm on Friday and another 27.7mm on Sunday." When I moved into my current place in 2005, it rained every day for 66 days. Plan for constant rain.

Be interesting to start a thread on here about getting data out of heat pumps. There are enough people, with different heat pumps, and a few people with good IT skills, should be possible to create a few basic packages that run on basic 'computers' and can store data. Leave the analysis up to the people that are interested, just create some text files of say electrical usage, run times (with timestamps) mass flow rate, flow and return temperatures, room temperature and outside air temperature.

These seem to give mixed results, especially with the electrical input numbers, which are critical.

With a raspberry pi. Some cheap 1wire temp sensors, a flow meter and something to read the electoral power input (see my blog).