This doesn't make sense - NYT article about a solar installation in the US

[NiHaoMike]

Running on generators is contradictory to the goal of reduced emissions.  That would be the absolute worst way to provide power.

It would happen rarely so not much in the grand scheme. Also, it means that the first ones to get dropped for demand reduction should the grid get crippled would be the ones prepared to deal with it. Additionally, there could be different amounts of reward given and/or different priorities depending on the kind of generator, more for generators that run from renewables such as biodiesel or wind/solar. There could also be a separate incentive program for CHP generators in cold areas, to export to the grid when demand is high and get paid for that, with the excess heat stored as hot water for later use.

Work from home is pretty popular and I'll bet houses are more efficient than office buildings because the workers pay their own utility bills.  A laptop doesn't require all the features of the modern office building.  I think I would work from the patio for about half the year.  Poke at a spreadsheet while watching the dogs run and play.  Pretty easy life!

Likely to be true in areas where HVAC is rarely used, otherwise it would use far less energy to heat/cool an office building instead of many houses, even under the assumption that not all houses would be unoccupied during the day. Where there would be a huge energy savings would be the reduction in driving.

[Someone]

For all the talk of moving to electric transport there hasn't been any planning on how the grid will support that and where the generation will come from. Technically possible, yes, but the free market won't deliver it as the current market they play in is largely for show/theatrical (monopoly distributors, cartel generators).

None of the electric public utility systems in the US are 'free market'.  They are all controlled by Public Utility Commissions.  The PUCs tell the utility what to do, when to do it and how much extra they can charge for the results.

Which is what I said, they arent actually market driven.

Most people work during on-peak hours, that's why the demand is called 'on-peak'; buildings are up and running.  Charging at home, after work, will be during a period of reduced demand.  But, not to worry, if things get out of hand, the utilities will move to Time Of Day billing.  They already have tariffs (regulations) in place and the rates are available as an option (at least here in Northern California with PG&E).  They will just convert everybody.  For the most part, the revenue meters have already been converted to Smart Meters which are read over the power line so getting instantaneous or interval demand is trivial.  You may note that there hasn't been a meter reader (person) in the neighborhood for a decade or more.

Current time of use tariffs are barely connected to the live cost of energy, at most I've seen a 2 season split. So the tariffs are a heavily averaged guess of the average cost, still noting to incentivise people to use less power when supply (or delivery) is constrained. Only moving people to the average time of day when its typically less constrained.

The peak demands (as cause outages/curtailments) are currently derived from mass use of electric HVAC, a big part of average energy use:
http://www.withouthotair.com/c18/page_103.shtml
Time of use is not solving that and won't squeeze the future EV demand into the excess generation available.

EVs already have a programmable start time (or end time) as part of the firmware.  That's cool!  Tell the car you want it fully charged by the time you finish your cup of coffee in the morning (end time) and it will start the charging as required.  It remains for the car owner to have a large enough charger to get it done.

That may help with the delivery (network) constraints, but doesn't explain where the new generation capacity will magically come from. Cars are quicker to build and deploy than power plants, plans/policy is in place to require electric transport, but there is no matching policy or plan to increase generation.

Gasoline here is $5/gallon and if a car gets 20 MPG, that's about $0.25/mile.  If we take 3.7 miles per kWh and $0.25/kWh this works out to $0.07/mile.

US is on the low end of electricity pricing relative to petrol when compared worldwide:
https://www.eevblog.com/forum/chat/problems-if-we-all-had-tesla-cars/msg705793/#msg705793
And you take the classic EV-nut approach of your choice car designed for energy efficiency shall be compared to gas guzzling bricks, instead of other vehicles designed for energy efficiency (50-60MPG). So keep convincing yourself, but its just the same old reality distortion.

You're in a pricing structure (low road tax, flat(tened) electricity) that encourages you to use those supplies (roads and electricity) for your advantage and pushing the costs equally onto everyone else (in the state/country). Its the opposite of a market, and with insufficient personal disincentives the system lacks negative feedback and is almost certain to fail (traffic jams, blackouts).

[Someone]

There could also be a separate incentive program for CHP generators in cold areas, to export to the grid when demand is high and get paid for that, with the excess heat stored as hot water for later use.

This is one possibility that could make a big dent in generation and network inadequacies as (above) the worst peak demands on the electricity grid are almost entirely from space heating/cooling. There are groups looking at larger commercial and community/district sized CHP/trigeneration too.

[NiHaoMike]

The peak demands (as cause outages/curtailments) are currently derived from mass use of electric HVAC, a big part of average energy use:

That can be economically solved by adding thermal storage (particularly for air conditioning which can be stored as ice), but there needs to be incentives to build it.

[james_s]

Likely to be true in areas where HVAC is rarely used, otherwise it would use far less energy to heat/cool an office building instead of many houses, even under the assumption that not all houses would be unoccupied during the day. Where there would be a huge energy savings would be the reduction in driving.

Probably a lot less difference than you might expect. Besides, even if everyone is in the office building they can't all just stop heating and cooling their houses. A large number of people have pets and they are generally comfortable under the same sort of conditions that humans are comfortable, you shouldn't let your house get scorching hot or freezing cold if your dog or cat is home. Then there is the fact that if you set back the HVAC deeply you have to play catch up and run it longer to get the temperature comfortable when you get home. Deep setbacks only really make sense if you are away for multiple days.

Regarding storing air conditioning as ice, calculate how much ice you need to store say 6 hours of 36,000 BTU/hr, so over 200k BTUs of cooling for a modest house in a moderate climate.

[james_s]

The question I have is how prepared was Texas in regards to being able to charge and run all those cars? The power supply seems to have coped. Unless it snows, of course. 

Disasters happen. We had a massive storm blow through here about 15 years ago that knocked down multiple large transmission lines and caused widespread power outages lasting well over a week. People couldn't get gas for their cars because the gas stations didn't have power to pump the fuel. It was not really any different vs people not having power to charge EVs. You can't plan everything around the sort of events that happen once in a century.

[station240]

Good old Ohms law is responsible for most of the problems in this article.

You have two power sources:
1) Grid, 112V very low impedance.
2) Solar Inverter, 112V low impedance.
Note, this doesn't work as intended, as the grid has much lower impedance, also add in the losses into the transformer.
So the Solar inverters boost the voltage, say to 113V or even 115V, so current is drawn from the inverter instead.

However, there is a maximum voltage for the street grid, to avoid damage.
So at some point the solar inverters will shut down, and stop outputting power.
So the power companies have choices to make:
1) Limit how many kW of solar is on a particular street transformer. or;
2) Alter the tap on the transformer to output a lower voltage to start with (or just install new transformer anyway.
3) Install a transformer with auto tap changer.

Oh yeah, and likely some of these transformers needed replacing anyway, as too close to being overloaded or just old.
I suspect the US isn't doing themselves any favors by using 110V AC, as the extra losses in cables mean more transformers and less houses on each to even out the load.

As most of these problems exist in other parts of the world, there are solutions:
1) Demand management, digitally broadcast to homes when there is an over/under supply of power in their area. Whatever automatic system is in place can offer to increase/reduce by X kW, requires say fiber optic internet for low latency.
2) Neighborhood battery storage, install batteries to soak up excess power and sell it back at night. Only profitable if not charged utility fees, and the power company don't like that or others making money.
3) Install two separate inverters in houses, so solar/battery power still runs the house in cases of high grid voltage/blackouts. Some power companies don't like off-grid power solutions like this.

Personally I like the Neighborhood battery, it can work well, helps everyone not just those with their own solar/batteries.
Problem is it's not profitable if the power company want full line fees for sending power maybe 200 meters tops, as it's paid twice as in/out and isn't large scale.
Can also be setup as a way to "bank" power, generate excess during the day, get it back at night at the same price.
Could also be wired up to power the entire street to prevent blackouts, just switch the transformer out to prevent backfeed.

[NiHaoMike]

Probably a lot less difference than you might expect. Besides, even if everyone is in the office building they can't all just stop heating and cooling their houses. A large number of people have pets and they are generally comfortable under the same sort of conditions that humans are comfortable, you shouldn't let your house get scorching hot or freezing cold if your dog or cat is home.

You could only heat or cool the room they're in.

Regarding storing air conditioning as ice, calculate how much ice you need to store say 6 hours of 36,000 BTU/hr, so over 200k BTUs of cooling for a modest house in a moderate climate.

It would be far more practical than using batteries to power air conditioners, it turns out that pound per pound, ice would store about the same as using batteries to operate air conditioners, but the ice is a few orders of magnitude cheaper, has no inherent limitation on lifetime, can be left at any "state of charge" for extended periods of time without degradation, and can be cycled indefinitely. The only real disadvantages are that it's only useful for HVAC (so not a complete replacement for batteries) and (for now) the lack of premade solutions that use it.

One ton of ice (about 1 "IBC tote" worth) would provide 288 kBTU of cooling, that's already more than your example.

[Someone]

As most of these problems exist in other parts of the world, there are solutions:
1) Demand management, digitally broadcast to homes when there is an over/under supply of power in their area. Whatever automatic system is in place can offer to increase/reduce by X kW, requires say fiber optic internet for low latency.

I believe that one came up on the forum before, but will repost the original here:
https://arstechnica.com/tech-policy/2021/06/texans-regret-opting-into-power-plan-that-remotely-raises-thermostat-temps/
Consumer received (likely upfront one-off) payment to participate in minor load shedding, then goes mental when thermostat is raised to 78° F (26° C) from 74° F (24° C).

You'd be amazed how demanding of absolute/selfish convenience the general public are. "why should I slightly modify my behaviour if its for the benefit of others" while completely ignoring the non-linear cost/inconvenience of complete failure/blackout.

[Siwastaja]

Disasters happen. We had a massive storm blow through here about 15 years ago that knocked down multiple large transmission lines and caused widespread power outages lasting well over a week. People couldn't get gas for their cars because the gas stations didn't have power to pump the fuel. It was not really any different vs people not having power to charge EVs. You can't plan everything around the sort of events that happen once in a century.

Yes, and often the best mitigation strategies are very simple and low-cost. For example, in Texas, owning some warm clothes just in case even though they consume 2 sq ft of valuable closet space.

[Siwastaja]

NiHaoMike's ice storage has the problem of mechanical complexity, including how the ice is separated from the evaporator coil, then transferred into insulated storage, and so on.

But if you can accept lower storage energy density, forget about utilizing the latent heat and only use sensible heat, i.e., go for liquid water. It has a long and very successful track record of being used for thermal energy storage, and energy can be trivially transferred with water pumps. It's almost too easy.

But yeah, for cooling (or for high-COP heating), the dT can't be much (say 10K) which is an energy density sacrifice. Gravimetric energy density is close to that of lead acid batteries (some 20Wh/kg actual), and volumetric even worse. But whenever you have excess space in your basement, i.e., don't live in some big city with expensive land cost, why the heck not.

I do exactly that, store heating energy in water at quite low dT, but clearly my 1200liter tank is too small for what I really want to do. What's actually needed is in order of 5m^3. This translates into approx. 2-3m^2 of hopefully not too valuable area in your basement.

[NiHaoMike]

NiHaoMike's ice storage has the problem of mechanical complexity, including how the ice is separated from the evaporator coil, then transferred into insulated storage, and so on.

Just put a loop of copper tubing in the tank, problem solved.

[Marco]

NiHaoMike's ice storage has the problem of mechanical complexity, including how the ice is separated from the evaporator coil, then transferred into insulated storage, and so on.

For hydronic not all that much. Instead of directly pumping through your storage tank, the heat pump has its own propylene glycol loop with two heat exchangers in the tank, one for each loop. Need 1 extra pump.

Just make the surface area on the heat exchanger large enough and finely enough distributed you can freeze the water in place. Dealing with the expansion will take a bit of engineering.

[Siwastaja]

Freezing water is well known to burst pipes so I guess it would be non-trivial dealing with that.

The glycol solution inside the pipe won't freeze, but the water in tank would need to freeze; result is the same. I'm suspicious how to handle that force. Strong thick walled pipes could do it. Then the tank walls must cope with the force as well. OK, make it out of 10mm thick steel and weld reinforcements.

But no matter how strong you make everything, the expanding ice has to go somewhere. I guess when the structures are strong enough, then the ice just crushes itself. OK, let's call that sorted out.

But then again ice has worse thermal conductivity than liquid water (seems to be about one quarter) and even more importantly, within ice, natural or forced convection becomes impossible. So the ice first forms on the tubing, but as the layer thickness increases, power transfer worsens, or the transfer liquid inside pipes must be made even colder to compensate, worsening the COP.

This necessitates that the whole storage tank must be full of that strong pipework, because ice can be only generated within short distance (maybe a centimeter / half an inch?) of the pipe with good efficiency or rate (power). You can see this effect in action by noticing how about an inch of ice that has formed on the evaporator of a refrigerator already decreases the efficiency of the unit to the point it's constantly operating and still temperature inside starts to rise.

You can't use traditional expansion tanks either.

I just can't see how this is easy or trivial. I'm not saying it's impossible, though. Great engineering challenge.

And the prize is high if you can do it, at 334 kJ/kg ~= 0.1kWh/kg = 90 kWh/1000kg it would allow quite nice energy density compared to just using sensible heat; with cooling you would be limited to just dT=10degC which means 42kJ/kg = 12kWh/1000kg.

And to give you an idea how much force freezing water can generate, that's how exposed bedrock erodes in cold climates. Water seeps in tiny gaps and this is strong enough to crack the rock.

[rstofer]

As most of these problems exist in other parts of the world, there are solutions:
1) Demand management, digitally broadcast to homes when there is an over/under supply of power in their area. Whatever automatic system is in place can offer to increase/reduce by X kW, requires say fiber optic internet for low latency.

I believe that one came up on the forum before, but will repost the original here:
https://arstechnica.com/tech-policy/2021/06/texans-regret-opting-into-power-plan-that-remotely-raises-thermostat-temps/
Consumer received (likely upfront one-off) payment to participate in minor load shedding, then goes mental when thermostat is raised to 78° F (26° C) from 74° F (24° C).

You'd be amazed how demanding of absolute/selfish convenience the general public are. "why should I slightly modify my behaviour if its for the benefit of others" while completely ignoring the non-linear cost/inconvenience of complete failure/blackout.

Our utility has a scheme for remotely shutting down HVAC units for brief periods when system demand is high.  During these brief high demand periods, HVAC compressors are locked out for up to 15 minutes every half hour.  The program is voluntary and has some rewards.

https://www.pge.com/en_US/residential/save-energy-money/savings-solutions-and-rebates/smart-ac/program-faq/smartac-program-faq.page

[james_s]

How do they stop people from simply bypassing the thing once they've signed up to get the benefits? Air conditioners are simple enough devices I don't see what they could do to lock out the compressor that wouldn't be trivial to bypass. You can even push in the contactor with a screwdriver and the compressor will start up.

[Marco]

Freezing water is well known to burst pipes so I guess it would be non-trivial dealing with that.

There's already systems out there for non residential use, so I assume they solved it.

You could put lots of air filled flexible hoses in the water volume and along the container wall (no need for steel then) to give the pressure somewhere to go perhaps?

[Bassman59]

Probably a lot less difference than you might expect. Besides, even if everyone is in the office building they can't all just stop heating and cooling their houses. A large number of people have pets and they are generally comfortable under the same sort of conditions that humans are comfortable, you shouldn't let your house get scorching hot or freezing cold if your dog or cat is home.

You could only heat or cool the room they're in.

Regarding storing air conditioning as ice, calculate how much ice you need to store say 6 hours of 36,000 BTU/hr, so over 200k BTUs of cooling for a modest house in a moderate climate.

It would be far more practical than using batteries to power air conditioners, it turns out that pound per pound, ice would store about the same as using batteries to operate air conditioners, but the ice is a few orders of magnitude cheaper, has no inherent limitation on lifetime, can be left at any "state of charge" for extended periods of time without degradation, and can be cycled indefinitely. The only real disadvantages are that it's only useful for HVAC (so not a complete replacement for batteries) and (for now) the lack of premade solutions that use it.

One ton of ice (about 1 "IBC tote" worth) would provide 288 kBTU of cooling, that's already more than your example.

Where am I going to store this water?

[bson]

Of course the grid needs to be upgraded to handle a large number of small power providers.  The problem is if you upgrade it people will consume more power, and that's bad.  PG&E's profits are decoupled from its energy sales, so it has no incentive to sell more.  Just about everyone with an interest in energy conservation are opposed to investing in anything that might cause more energy consumption, regardless of whether it's to charge a Tesla or run a heater.  This of course makes sense, because the incremental power for every new Tesla plugged in comes from a fossil-fuel generator somewhere.

[thm_w]

How do they stop people from simply bypassing the thing once they've signed up to get the benefits? Air conditioners are simple enough devices I don't see what they could do to lock out the compressor that wouldn't be trivial to bypass. You can even push in the contactor with a screwdriver and the compressor will start up.

What stops you from just bypassing your electrical meter and not paying for electricity at all.

[james_s]

How do they stop people from simply bypassing the thing once they've signed up to get the benefits? Air conditioners are simple enough devices I don't see what they could do to lock out the compressor that wouldn't be trivial to bypass. You can even push in the contactor with a screwdriver and the compressor will start up.

What stops you from just bypassing your electrical meter and not paying for electricity at all.

The box is tagged with a special tamper evident seal. Theft of electricity is a serious crime and they have ways of detecting it. I don't think running the AC when it's supposed to be locked out is a crime, certainly it is not theft and I suspect would be much harder to detect. You're still paying for the electricity.

[bdunham7]

Theft of electricity is a serious crime and they have ways of detecting it.

Here in SoCal (or the Bay Area) there are no serious crimes anymore.  Just wayward souls crying out for help by shoplifting and driving drunk.  I can't prove it, but I suspect that in some places theft of electricity is as rampant as any third world country--and if it isnt', it's only because nobody is smart enough to pull it off.

[rstofer]

How do they stop people from simply bypassing the thing once they've signed up to get the benefits? Air conditioners are simple enough devices I don't see what they could do to lock out the compressor that wouldn't be trivial to bypass. You can even push in the contactor with a screwdriver and the compressor will start up.

What stops you from just bypassing your electrical meter and not paying for electricity at all.

The box is tagged with a special tamper evident seal. Theft of electricity is a serious crime and they have ways of detecting it. I don't think running the AC when it's supposed to be locked out is a crime, certainly it is not theft and I suspect would be much harder to detect. You're still paying for the electricity.

In terms of the HVAC, the utility could look at the demand on the revenue meter and expect a reduction from not running the compressor.  If they didn't see the reduction, they could make a pretty good guess.

As to bypassing the revenue meter:  The utility has a lot of comparative information.  If you 3,000 sf house is using demonstrably less energy than your next door neighbors 3000 sf house, they might start to suspect something.

A lot of people have used inductive coupling from overhead HV lines and that too is theft:

https://www.industrytap.com/electromagnetic-harvesters-free-lunch-or-theft/1805

There's nothing new here, every possible scheme has been tried and detected.  The utilities employ some pretty bright folks.

[rstofer]

  Just about everyone with an interest in energy conservation are opposed to investing in anything that might cause more energy consumption, regardless of whether it's to charge a Tesla or run a heater.  This of course makes sense, because the incremental power for every new Tesla plugged in comes from a fossil-fuel generator somewhere.

You're overlooking nuclear.  There are still 93 operating nuclear reactors in the US.  Mostly on the east coast.

[Someone]

Just about everyone with an interest in energy conservation are opposed to investing in anything that might cause more energy consumption, regardless of whether it's to charge a Tesla or run a heater.  This of course makes sense, because the incremental power for every new Tesla plugged in comes from a fossil-fuel generator somewhere.

You're overlooking nuclear.  There are still 93 operating nuclear reactors in the US.  Mostly on the east coast.

Nuclear, which runs almost perfect capacity factor, no way no how. Its not the excess capacity in the grid sitting idle just waiting for demand, that'd be the coal (seasonal) and hydro or gas (short term) plants.