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Microwave-powered home boiler
- compressedgas 6y ago> They say the boiler is 84% efficient in converting electricity into hot water, and another 12% of waste heat is recycled, giving a total efficiency of 96%. An electric water heater is 100% efficient.
- SigmundA 6y agoRight, trying to see some reason why heating water with microwaves would be preferable to standard resistive heating elements other than for marketing purposes.
- mjlee 6y agoCharitably, it's less prone to limescale insulating the elements, increasing service life and making the system more efficient as you don't need to run water as long waiting for it to heat up.
- SigmundA 6y agoWhy is it less prone to scale buildup? Scale comes from heating the water, which both do. I have a gas instant hot water heater, with a water softener it basically never builds up scale, otherwise a yearly acid flush is recommended and it has flush port that make it a easy job.
- dTal 6y agoScale builds up on the heating elements because it precipitates out when the water turns briefly to gas. Once present, the scale will negatively impact the coefficient of heat transfer between the element and the water. A microwave system wouldn't have any heating elements, and any precipitates would fall harmlessly to the bottom, not hurting efficiency.
- rich_sasha 6y agoI guess that already exists so can't launch as a new product. I think it's called 'immersion heater' in the UK. Most homes have one already in fact, as a backup for when the boiler breaks.
- msandford 6y agoThink of all the delightfully higher upfront costs vs standard immersion heating elements plus also the ongoing maintenance! It's a veritable gold-mine. My guess is that's why.
- api 6y agoResistive heaters easily get encrusted in limescale, often causing them to fail. My guess is this can be near zero maintenance.
- njb311 6y agoThe article doesn’t say it explicitly, but I’m assuming it heats water on demand, rather than heating a tank which immersion heaters do. You can buy a resistive element electric shower that gives instant hot water and requires up to about 10kW (and costs £100-200 not £3500) but a gas central heating boiler might pump out 22-30kW equivalent of heat. You would need modifications to your electricity supply to achieve that with electric heaters. If the microwave technology was able to give better performance that would be in its favour, but the boiler cost is not competitive (like many new products). Air source heat pumps are more efficient but again the purchase/install costs make the return on investment long, it was going to be more than 40 years in my case (unless of course carbon pricing changed the calculation), which may be longer than the lifetime of the unit. You also have to be mindful of the refrigerant used in ASHPs because if it leaks the warming potential is several tonnes of CO2e, thankfully a lot of change is happening there too. What will make the difference to all this is the combination of increased efficiency plus production at scale that makes retrofitting attractive to homeowners. Part of that scale could come from mandatory fitting of such equipment to all new builds.
- SigmundA 6y agoResistive heating is 100% efficient, they are saying 96% for microwave, meaning you will need 4% more power to achieve the same heating either in a tank or no tank.
- njb311 6y agoYes, I wasn’t suggesting that this solution was more efficient, but that solutions that are more efficient than what they replace are what we should be focusing on. It’s fine to say that resistive is 100% efficient, but my point was that a 10kW instant electric heater is not enough to meet the demands of many households (and falls well short of a gas boiler output) and you can’t just say install a 20kW electric heater because typically household supply is not built for that. And so if you heat a tank of water (a typical immersion heater is 3kW) then all of a sudden you have heat loss and you are nowhere near 100% efficient.
- 6y ago
- jnsaff2 6y agoAlso water heater using a heat pump is 200-500% efficient.
- overscore 6y agoAnd electric heat pumps can be 350% efficient. However, the USP of this product is that it's a drop-in replacement for existing gas boilers which are prevalent in some parts of the world. The article says the unit costs around £3,500 and installation of a replacement gas boiler costs around £500, so maybe ~£4,000 to switch from gas to electric. An equivalent air-source heat pump installation could easily cost £12,000, and often gas boilers are located in areas which are space-constrained.
- dTal 6y agoNot really. The boiler would need perfect insulation for that to be true, which is theoretically impossible.
- rich_sasha 6y agoThis is as zero-emission as the grid, simply having someone else burn fossil fuels doesn't make it clean (it's probably better but still). Also gas is a lot cheaper to heat with at current UK prices than electricity. One of the reasons heat pumps are used is that the increased efficiency offsets that.
- deeesstoronto 6y agoelectric boilers at 100% efficiency are also drop in replacements for gas boilers... They are just much more expensive to run then gas or a heat pump.
- MisterTea 6y ago> The creators of the world’s first microwave-powered boiler have said it can provide a straightforward, zero-emissions replacement for the gas boilers that heat most homes in the UK. > The boiler uses electricity to heat water which can then be pumped through existing radiators and to taps and showers and baths. What am I missing here? The novelty microwave part? There have been electric boilers for ages but no one buys them because electric heating is costly in most parts of the world, never mind the NY/NE area I live in. Though I think it is competitive in the Niagara region like Buffalo, NY or Toronto, ON. Though electric hot water heaters are not uncommon if the area does not have gas or apartments and so on.
- frosted-flakes 6y agoElectricity rates are the same across Ontario, and natural gas prices are mostly the same. I live near Toronto, and when I did the math a couple of years ago, an electric heat pump water heater would cost about 4x more to run than natural gas (back-of-the-envelope math). A resistive water heater would be even worse.
- mavhc 6y agoWhy would new houses be built without reversible heat pump/air conditioning installed? Isn't most of the cost in the retrofitting for existing houses? That's not the case for new houses, can put air pipes in as you design and build them
- mikewarot 6y agoThis (using an inefficient magnetron instead of 100% efficient resistive heat) is snake oil. Also: Here in the US, where I live.. running a water heater off of natural gas produces less CO2 than doing it off of the fossil fueled power grid, when all of the efficiencies are considered. Upgrading the grid to handle more current is going to eat up a lot of resources, but renewable power will help balance that out, so 20-30 years out, electric resistive heat won't be as awful a choice as it would be right now.
- dTal 6y agoThe article explicitly says it doesn't use a magnetron, but rather "precise solid-state microwave generators... which can be tuned specifically to heat water and better targeted [sic] than the magnetrons used in microwave ovens". (I'd have thought magnetrons counted as "solid state" too, as they have no moving parts, but still - they're very clear that's not what this is)
- mikewarot 6y agoMy bad... magnetrons are still the way to go for reliable high power microwaves... there's nothing "precise" required to heat water.