[stdgy]

Am I the only one that find this article incredibly confusing?

It starts off talking about wanting to move energy production to renewable sources. Great, I'm with you so far. A major issue with renewable energy (solar and wind) is that they're variable, not constant. This results in uneven power. The wind doesn't blow, it's cloudy or it's night time. So we need a way to convert this variable renewable energy into constant energy that's accessible around the clock. An obvious solution to the problem is to convert the renewable energy into stored potential energy. This is what pumped hydroelectric dams are all about. Use the variable energy to pump a bunch of water up behind a dam, then release it when you need a more constant supply of energy.

Great, so we've got that much figured out. The world needs a way to convert renewable energy into constant energy.

And the solution to this problem is... the distribution of more efficient water heaters.

Wat

How do more efficient water heaters in any way, shape or form help solve the renewable variable rate energy to constant energy problem? I feel like I must be missing something obvious. Are we able to somehow store energy in heat-pump based water heaters and then extract that energy to run other items in our homes? When you store energy in a heat-pump based water heater does it not need to run at night when renewable energy sources are lowest?

Can anyone explain to me what the heck this article is talking about?

I feel like I'm missing the larger picture, but I don't see how these two concepts (energy storage and appliance efficiency) are related.

[bluGill]

> How do more efficient water heaters in any way, shape or form help solve the renewable variable rate energy to constant energy problem? I feel like I must be missing something obvious

A large portion of our world energy use is to make heat. Thus if you can make the heat you need when there is plenty of renewable energy available, and then store it for use latter that is a large win. Sure we can't turn that heat back into electricity (false, but they are not worth talking about), but since heat is the goal that doesn't matter.

This is well understood. My parents have been on a off-peak water heating program since 1988 (in all those years they only ran out of hot water 5 times, and nobody was trying to save water). Based on that experience, just the hot water a family uses in a day is in the 300-800 liters range (go high - running out of hot water for the day sucks). Heating your house is a lot more though - 40000 liters is a low end estimate I've seen.

You won't be cooking food, powering your car, or lighting your house this way, but it is still a cheap and useful way to store energy. It is also something we can do for the world using yesterday's cheap technology.

[stdgy]

Good points! I'm certainly in favor of time-shifting demand to meet supply to maximally utilize renewables. Let's grab as much of this low hanging as we can.

I just thought the framework of his argument was rather odd. Better water heaters are framed as being a way to avoid constructing power storage systems that convert variable renewable energy into steady baseline power, which feels like an argument that doesn't hold up. We'll still need some way to supply steady power to run AC units, heaters, and other big power draws all night, no matter what type of water heaters we use!

[evandijk70]

The idea was that you run the water heaters at a time when demand for electricity is low, and supply is high. The water will stay warm for quite some time and can be used later. For example - run the water heater at 3am during a windy night, so people can shower in the morning

[_ph_]

The point is, that we can move demand around. The smart water-heaters with the ability to store heat are not only more efficient, they can be run when a lot of electricity is available and can be shut off, when there isn't. Yes, we also will need some amount of storage to produce electricity when demand exceeds production, moving the time of demand goes a long way on managing renewables.

[ZeroGravitas]

The big point is demand response in smart heaters allowing time shifting.

He also, confusingly, makes a second point about how efficiency can to avoid building powerplants/storage.

Replacing old inefficient heaters with new smart and efficient heaters is a double win.

If you power them from renewables it's a triple win.

Also night time energy is often low carbon because of nuclear and wind combined with low demand, but modern smart heaters can respond at a much smaller scale to use "excess" energy.

[derriz]

> The world needs a way to convert renewable energy into constant energy.

Not really or at least that represents a gross simplification of the situation.

Electricity demand is anything but constant - peak to trough intraday consumption can vary by up to a factor of 5. Grid engineering is all about matching lots of different sources with different generation characteristics with a varying (but quite predictable) demand curve.

All generation sources are intermittent - they are just intermittent in different ways. Solar and wind have well known limitations in this regard but at least the variation in output is predictable - particular solar, wind is typically accurately predictable up to a few weeks horizon.

The intermittency associated with thermal plants may be less in some ways but it has the disadvantage is that it is largely not predictable. For example, the average US coal plant will be unavailable for generation 15% of the time - so roughly 1 hour down for every 6 hours generating. Most of this 1 hour downtime is unscheduled/forced which is unpredictable. It's a myth that having a 1GW of fossil fuel generation capacity means you can reliability meet a peak demand of 1GW.

Also nuclear and coal are NOT good at load following - they operate most efficiently when producing the constant design output. Ramping up/down coal or nuclear output quickly is often not at all possible or is possible - depending on plant design - but with a large loss in efficiency and increased plant stresses and wear and tear.

Grid engineers have been maintaining this balancing act between unreliable generation and fluctuating demand for ever. In the past the focus was on coping with the intermittency caused by the failure modes of thermal plants. Increasingly now they are coping with the variable output of solar and wind generation but seem to be managing this - a bunch of European countries source more than 40% of their electricity from solar or wind and none required utility scale li-ion or have experienced increased grid instability.

The same tools are used to handle wind and solar intermittency as are used to handle thermal plant failure or inability to ramp up/down quickly - some hydro storage, backup idling natural gas plants, grid interconnections, etc.

Fundamentally the renewables revolution is happening quietly in the background is driven by simple economics. Coal and nuclear are just too expensive by a factor of 2 or 3 and natural gas, on-shore wind and utility scale solar are just so cheap in comparison. It's cheaper now to build a load of wind (or solar) and some backup natural gas generation - typically with a capacity factor of only 10% or so - than it is to meet demand with thermal fossil fuels. This is because wind and solar are capital intensive while NG plants are cheap to build but expensive to operate due to fuel costs. This combo (idling natural gas and wind and/or solar) is in the process of displacing everything else. 90% of the new generation capacity added in the US last year was of this nature. And a similar proportion is observed globally.

Meanwhile you have endless arguments about why wind and solar "cannot work" in fora, while all around the world it clearly IS working and analysis suggests it requires no technology breakthrough to get to 60%-70% carbon-free generation - many grids are well along this journey (40% to 50%) and none of the doomsday scenarios of massive load shedding, black-outs, etc. have occurred.

[ctdonath]

My utility solar cost average 50% over regular electricity $ for 2 years.

Texas suffered a doomsday scenario last winter, power demand far exceeding renewables ability under prolonged bad weather. California has frequent rolling blackouts; bizarrely, solar roofs are disallowed to supply the homes they cover.

[derriz]

Where in the world do you live out of interest? There must be some unusual local conditions that would cause that price discrepancy because I've followed the electricity prices in a number of European countries as they've increased their reliance on wind turbines and have seen no obvious kinks in the plots of prices as wind has contributed more and more. Certainly wholesale electricity prices - where I've followed them - are at a historic low at the moment but there is a lot on the demand side that could be causing this.

The Texas story actually reinforces one of my points - thermal fossil fuel plants are unreliable also as the failure of thermal plants caused a far greater loss in capacity than that lost by renewables.

California's electricity has been a mess for decades before the recent growth in solar and wind so I'm not sure how you can claim a causal relationship between what's happening now in California and the expansion of wind and solar.

Regarding domestic roof-top solar PV - I currently don't see it having any role to play in the march towards carbon-free energy - the cost per KWh is just too high and in many countries is only made viable by large government grants and feed-in tariff guarantees which effectively allow a domestic installation to exploit the grid like a giant infinite and free battery. Utility scale solar is completely different - it costs about 1/5 of the price per KWh compared to roof-top domestic PV and in many markets is now competing and beating conventional thermal generation on price without government support.

[oscardssmith]

The main cause of Texas's blackouts were the grid losing about 70% of their natural gas power (and not having good inter-connects with the rest of the US). Also, it is a great example of where the ability to pre-heat a ton of water would have been really useful. If they had the ability to do so, it would have greatly reduced the demands on the grid when the storm hit, which would have prevented the problem in the first place.

[judge2020]

Maybe this author has a stake in some up-and-coming smart water heater company whose sales pitch is that they only heat up the tanks when it would use only renewable energy?