battery grid feedback

[Hedges]

Part of that future is one in which they will see less revenue as more people generate their own power.

Electric utilities aren't in the power business. At least, they haven't been since our regulators forced them to divest power generation in the name of free markets.
What they are in is the business of distributing power over the electric grid, installing drops to consumers, and billing.

I think power transmission costs should be allocated on a more granular basis, for instance separating long-distance transmission from local. Both efficiency and maintenance issues differ.
If we shove power into the grid and it is consumed elsewhere on our side of the transformer, or somewhere else in the community, the utility ought to get a fee for the equipment used and the billing & customer support they provide.
Net metering would then incur a fee, according to where power is distributed and drawn from. Demand charges could also be rolled into our power purchases.

 

[Hedges]

The efficiency drops by about 40% from air temp of 80F to 50F with water temp of 80. And, no my calculations do not compare to running only at night but rather running at rate of $.25 vs $0.05. Then again, I have other benefits of having the batteries and the extra inverter. A ground source heatpump would be a tens-of-thousands project.

Dollar wise, a $0.15/kWh investment is only 25% efficient (drops 75%) to arbitrage between $0.05 and $0.25/kWh.
If the batteries last a decade bringing cost down to $0.05/kWh for storage, then the numbers get much better.

Efficiency drop of 40% means 60% the heat production.
$0.05/kWh / 60% = $0.083, still 1/3 the cost of $0.25/kWh during afternoon.
The reduced efficiency costs you $0.033/kWh (only on those coldest 40 degree nights). Bet your battery cost of power never gets that low.

So I still say simply running heatpump at night is most cost effective. Can you show otherwise?
A battery bank capable of running swimming pool heatpump for any useful length of time would be massive, compared to what you need for other purposes.

In my case, with morning rates $0.15 and late afternoon $0.50/kWh, rather than battery storage I figure it is a better deal to deliver 3.x kWh in the morning for credit to receive 1 kWh late afternoon. Even though DIY batteries should amortize out to much less than the $0.35 spread, a 200% increase in PV capacity is about the same investment.

What I've used for batteries is SunXtender AGM. I estimate $0.50/kWh if cycled to end of life, but I only expect to use 20% of they cycle life by the time they age out. The bank is undersized, usable capacity in kWh is about 1x the kW size of my PV (charge rate > 0.5C possible, but set to 0.2C) It is large enough to last the night (if I turn off unnecessary things), but it's main purpose is grid-forming and a buffer for daytime direct PV to loads, during occasional grid failures. Excess PV production is discarded (curtailed) during that operating mode. Most of the time, GT PV operates, and the battery inverters just silently maintain float.

 

[Ampster]

Electric utilities aren't in the power business.

I understand deregulation in California. I am in a CCA which technically provides the generation component of my bill. PG&E only gets paid for distribution based on the kWhs I consume. My point is that if I consume less through the meter by generating more and consuming that power, then PG&E will have less revenue. The trend has been to add a fixed component (MDCs) and charge a Non Bypassable Charge when I use power previously stored. I think that trend will continue and I support it within reason. My philosophy is to use the grid as backup when there is no solar production and to charge my EVs. I want a reliable grid.

 

[Hedges]

Yes, grid is reliable, maintained, affordable. It is the best solution for most customers. Some distributed generation and storage can be useful, with grid always available if those fail.
If everybody had PV, batteries, inverters, there would be a massive amount of support and repair required. Also many catastrophic failures. The cost, even for just GT PV, is 3x what utility scale costs.
Maybe if new construction roofs were of suitable style/orientation and free of obstructions, and if installation was done by utility/CCA/Co-op rather than sold to individuals, it could be more cost effective.

I think managing loads to utilize power when generated, rather than adding storage, has the most leverage for maximizing use of renewables. Charging of EVs will be a big part of that. Thermal storage could be another.
Demand charges, where you pay for the fact that during bad weather you need to utilize grid and generation but don't pay for it in fair weather, are in some way necessary. Managing loads will help avoid having to over-built generation by reducing peaks.

 

[minerva]

Dollar wise, a $0.15/kWh investment is only 25% efficient (drops 75%) to arbitrage between $0.05 and $0.25/kWh.
If the batteries last a decade bringing cost down to $0.05/kWh for storage, then the numbers get much better.

Efficiency drop of 40% means 60% the heat production.
$0.05/kWh / 60% = $0.083, still 1/3 the cost of $0.25/kWh during afternoon.
The reduced efficiency costs you $0.033/kWh (only on those coldest 40 degree nights). Bet your battery cost of power never gets that low.

So I still say simply running heatpump at night is most cost effective. Can you show otherwise?
A battery bank capable of running swimming pool heatpump for any useful length of time would be massive, compared to what you need for other purposes.

In my case, with morning rates $0.15 and late afternoon $0.50/kWh, rather than battery storage I figure it is a better deal to deliver 3.x kWh in the morning for credit to receive 1 kWh late afternoon. Even though DIY batteries should amortize out to much less than the $0.35 spread, a 200% increase in PV capacity is about the same investment.

What I've used for batteries is SunXtender AGM. I estimate $0.50/kWh if cycled to end of life, but I only expect to use 20% of they cycle life by the time they age out. The bank is undersized, usable capacity in kWh is about 1x the kW size of my PV (charge rate > 0.5C possible, but set to 0.2C) It is large enough to last the night (if I turn off unnecessary things), but it's main purpose is grid-forming and a buffer for daytime direct PV to loads, during occasional grid failures. Excess PV production is discarded (curtailed) during that operating mode. Most of the time, GT PV operates, and the battery inverters just silently maintain float.

Your calculations are right and this is not really a money maker. But. $0.033/kW is $0.50 per cycle for a 14kWh battery pack. $2,000 per 4000 cycles. At the very least, one can look at it as a backup system, which is free or cost very little. I can also consider selling some power at peak rates making $0.20/kWh but that would be at best a great area if not overtly against the rules.

 

[Ampster]

I think managing loads to utilize power when generated, rather than adding storage, has the most leverage for maximizing use of renewables. Charging of EVs will be a big part of that. Thermal storage could be another.
Demand charges, where you pay for the fact that during bad weather you need to utilize grid and generation but don't pay for it in fair weather, are in some way necessary. Managing loads will help avoid having to over-built generation by reducing peaks.

Interesting that you mention demand charges. I have recently read that in other states demand charges have been implemented for residential customers. That may be a fair way to allocate costs. As EVs become more ubiquitous managing their loads will become more important. The grid has the capacity from 11PM to 8AM and during mid day. The trick will be to utilize that capacity but not overload the grid when it is stressed. I am speaking of the classic duck curve in California.

 

[Hedges]

Evacuated tube solar collectors might be something else to look at.
For late-season use, would be a steep angle to catch the sun.
Not trying to make high temperatures, so rather than heatpipe inside, maybe just water as working fluid. Either drain-back or antifreeze solution.

At least for small water volume heating, could be PV is more cost effective than thermal these days. In your case pool heating is probably a massive consumer, so might make sense.

I think unglazed flat plate collectors are the most efficient with small temperature differential, but for your 40 degree delta the evacuated tube collectors might be a good fit.

 

[fafrd]

Interesting that you mention demand charges. I have recently read that in other states demand charges have been implemented for residential customers. That may be a fair way to allocate costs. As EVs become more ubiquitous managing their loads will become more important. The grid has the capacity from 11PM to 8AM and during mid day. The trick will be to utilize that capacity but not overload the grid when it is stressed. I am speaking of the classic duck curve in California.

It’ll be interesting to see where this is headed in CA.

I’m fine with a fixed minimum fee for hook-up/access to the grid and I’m fine with grid energy being charged differently based on TOU and possibly even peak power used (of the fixed monthly charges could be different based on what level of peak power you want available to you when needed).

But as you round the corner and add storage, there is an upper limit to how high those fees can go before you say ‘screw it, I’ll go off grid and use a propane generator to plug the holes during rainy spells’.

I helped my brother set up an off-grid PV system at his vacation home in the boonies (where he’s been getting by off of his generator).

Once storage is cheap enough, it’ll be more economical to cut the cord if the California utilities keep going the way they are going…

 

[Hedges]

Of course the "Duck Curve" is a lie, conceived to penalize PV producers even though their valuable electricity offsets a massive amount of what would otherwise be fossil fuel powered electric generation.

The real "curve" is a flat line, power production exactly matches consumption.

The duck curve is what you get when you subtract PV production from total consumption, showing what power is generated from sources other than PV.
You can create many such curves. If you subtract nuclear baseline from total consumption, you get a massive peak right in the middle of the afternoon (just when PV is able to produce a lot of power, contributing a great deal to the grid and avoidance of CO2 emissions.)
Every power source has its own associated curve. PV is unique in that it does a better job of matching (summer) demand. Although, array oriented due South is not a perfect match to A/C loads; a bit of a Westward orientation would be better.

The utilities bemoan the duck curve, which requires them to spend $$ starting natural gas peaker plants ($100K, they say), then rapidly ramping up output for the neck of the duck.
I don't think gas turbines, once spun up to RPM, have any trouble increasing wattage output. Just feed more fuel.
If it weren't for PV, the utility would still have to start up the peaker plant every day. Power output would have to reach a higher peak, and total kWh production would be higher.
I think the actual objection of the utilities is that they get to produce fewer total kWh from the natural gas peaker plants (which means burning less fuel.) Running a generator is profitable, and the resent having demand reduced.

 

[Ampster]

But as you round the corner and add storage, there is an upper limit to how high those fees can go before you say ‘screw it, I’ll go off grid and use a propane generator to plug the holes during rainy spells’.

That is known as the death spiral for utilities. I am at that point of indifference and my strategy is to consume less from the grid and self consume more of my generation. Fortunately I have two controllable loads in the form of two EVs.

 

[fafrd]

Speaking of lower-cost storage in the future: https://spectrum.ieee.org/gravity-energy-storage-will-show-its-potential-in-2021

 

[fafrd]

That is known as the death spiral for utilities. I am at that point of indifference and my strategy is to consume less from the grid and self consume more of my generation. Fortunately I have two controllable loads in the form of two EVs.

I’m preparing to follow in your footsteps (and am indifferent as well). My new system is designed to offset self-consumption so that I retain more of the credits from my grid-tied NEM array to be used to charge an EV in our future (~2023).

In total, I now have enough PV on the roof to power over a full day’s consumption even through the shortest days of winter.

So from that point, it’s only a question of how many day’s worth of battery storage you can afford and what your back-up plan will be to get through a stormy patch lasting longer than that (ie: backup generator).

Of course truly cutting the cord means investing in a much more powerful and reliable inverter than the two cheapo 1kW GTIL inverters I have now, but the point is that it’s within reach and involves a quantifiable cost…

 

[Ampster]

Of course the "Duck Curve" is a lie

It is what it is. It is a chart of two sets of data. To me it is a graphic that illustrates some market situations unique to California. If there are any inaccuracies it would be that rooftop solar only shows as a net reduction of consumption. In my case my consumption actually increases during the day because I often charge my EVs then.

 

[Hedges]

I use battery and inverter for grid-forming during utility failures.
The rotating machinery of nuclear and hydro on the grid should be ideal for grid-forming.
Nuclear runs at constant power output, while hydro is variable.
Ideally we could reach the point of all power sometimes coming from PV except for that nuclear baseline. That needs enough control of the distributed PV to remain stable.
Problem will be heating in winter. Wind may be able to supply some large portion of that in some areas.

The spread between wholesale and retail makes the inefficiencies of stand-alone alternative energy systems worth ignoring.

Speaking of lower-cost storage in the future: https://spectrum.ieee.org/gravity-energy-storage-will-show-its-potential-in-2021

Much smaller and more complex than a reservoir and hydro turbine.
Volume required for storage is proportional to hydro (with a multiple for density and height.)
Hydro, you only manufacture the something of the needed surface area, or plug at one end of a canyon. The volume and weight is water.
So I see crane lifting heavy containers as a niche system, and relatively small kW size at that.

 

[fafrd]

I use battery and inverter for grid-forming during utility failures.
The rotating machinery of nuclear and hydro on the grid should be ideal for grid-forming.
Nuclear runs at constant power output, while hydro is variable.
Ideally we could reach the point of all power sometimes coming from PV except for that nuclear baseline. That needs enough control of the distributed PV to remain stable.
Problem will be heating in winter. Wind may be able to supply some large portion of that in some areas.

The spread between wholesale and retail makes the inefficiencies of stand-alone alternative energy systems worth ignoring.



Much smaller and more complex than a reservoir and hydro turbine.
Volume required for storage is proportional to hydro (with a multiple for density and height.)
Hydro, you only manufacture the something of the needed surface area, or plug at one end of a canyon. The volume and weight is water.
So I see crane lifting heavy containers as a niche system, and relatively small kW size at that.

Oh, I was thinking about the future of domestic storage…

But I guess 50 barrels of concrete to equal just one Tesla powerwall isn’t all that attractive: https://www.google.com/amp/s/www.wired.com/story/battery-built-from-concrete/amp

 

[GXMnow]

I have to agree that the utilities are all big complainers. A few years ago, my home town got into this huge "Save Water" campaign. The hit us with limits for lawn watering, gave incentives for low flow faucets and toilets, and even had a program to help change out landscaping for reduced water use. So what ended up happening? The water consumption in the valley dropped over 40%. The program was a huge success. Sounds good, right? Well, the water company was not happy. Their revenue dropped by that 40%. So they not only raised our cost per gallon, they also added a few fixed charges to everyone. The end result, I cut my water use well over 20%, but ended up paying a little more on my water bill. If you cut 30% is was about a break even, and those who did cut 40% are still saving, but just a little.

I see the same thing going on with electricity. The less we buy from them, the more they are going to charge for it. My math on the payoff of my initial solar install got thrown out the window. I used to have a tiered rate with tier 1 at just $0.12 per KWH. With the amount of solar I installed, I figured I would stay completely in that tier 1 on all but the worst month of clouds and my A/C running. Using that figure, my system would have paid off in 6 years. But no, all new solar installs get forced to the time of use rate. And the cheapest rate starts at $0.17 per KWH. So even if I only used power at the cheapest time of day, it is at 42% more expensive per KWH. Then when the sun is going down, it jumps to $0.43 per KWH. Even if I am using very little power. That is a a 258% increase over my old Tier 1 rate. So my payoff is more like 10 years instead of 6.

When you go by their math, the higher electric rate actually made my system worth that much more. This is the B.S. the solar lease people like to use. As the electric rate goes up, you are saving more money. NOPE. It does not work like that. Had I not put in the solar, I would still be on the old tiered rate schedule. Of course, that was a grandfathered rate plan. If I ripped out the solar, and went back to a tiered plan, they jacked the rates there s well. The cheapest tiered rate 1 is now up to $0.26 per KWH. OUCH!

Now if you want to use gravity energy storage, GO BIG!!

Los Angeles considers $3B pumped storage project at Hoover Dam

The city's municipal utility is studying the potential of using the dam as a giant pumped hydropower plant run by renewables.

www.utilitydive.com

The idea is quite simple. Install solar powered pumps to push water back up into Lake Meade when the sun is shining, and then letting it generate through the existing dam. I like it. 3 billion does seem a bit pricey though. You do need some serious pumps to push water UP over 700 feet. And it will take a lot of solar to power that. But 3 BILLION, that sound like the $40,000 military hammer.

 

[Hedges]

$3 billion spread over a few million residents is less than even the city permits to put PV on rooftops.
Not clear how many kW or kWh involved. But this could be more cost effective than almost anything else grid-attached storage or PV related.

$3 billion isn't much more than chump change. In Mountain View, $100 million only bought one highway interchange for 85/101/Shoreline.
(I had noted before that existing overpass from 85 was wide enough for two lanes, but paint narrowed us down to 1 lane. I'll bet the commuters clamored for taxes to fund the new interchange.)

 

[fafrd]

I have to agree that the utilities are all big complainers. A few years ago, my home town got into this huge "Save Water" campaign. The hit us with limits for lawn watering, gave incentives for low flow faucets and toilets, and even had a program to help change out landscaping for reduced water use. So what ended up happening? The water consumption in the valley dropped over 40%. The program was a huge success. Sounds good, right? Well, the water company was not happy. Their revenue dropped by that 40%. So they not only raised our cost per gallon, they also added a few fixed charges to everyone. The end result, I cut my water use well over 20%, but ended up paying a little more on my water bill. If you cut 30% is was about a break even, and those who did cut 40% are still saving, but just a little.

I see the same thing going on with electricity. The less we buy from them, the more they are going to charge for it. My math on the payoff of my initial solar install got thrown out the window. I used to have a tiered rate with tier 1 at just $0.12 per KWH. With the amount of solar I installed, I figured I would stay completely in that tier 1 on all but the worst month of clouds and my A/C running. Using that figure, my system would have paid off in 6 years. But no, all new solar installs get forced to the time of use rate. And the cheapest rate starts at $0.17 per KWH. So even if I only used power at the cheapest time of day, it is at 42% more expensive per KWH. Then when the sun is going down, it jumps to $0.43 per KWH. Even if I am using very little power. That is a a 258% increase over my old Tier 1 rate. So my payoff is more like 10 years instead of 6.

When you go by their math, the higher electric rate actually made my system worth that much more. This is the B.S. the solar lease people like to use. As the electric rate goes up, you are saving more money. NOPE. It does not work like that. Had I not put in the solar, I would still be on the old tiered rate schedule. Of course, that was a grandfathered rate plan. If I ripped out the solar, and went back to a tiered plan, they jacked the rates there s well. The cheapest tiered rate 1 is now up to $0.26 per KWH. OUCH!

Now if you want to use gravity energy storage, GO BIG!!

Los Angeles considers $3B pumped storage project at Hoover Dam

The city's municipal utility is studying the potential of using the dam as a giant pumped hydropower plant run by renewables.

www.utilitydive.com

The idea is quite simple. Install solar powered pumps to push water back up into Lake Meade when the sun is shining, and then letting it generate through the existing dam. I like it. 3 billion does seem a bit pricey though. You do need some serious pumps to push water UP over 700 feet. And it will take a lot of solar to power that. But 3 BILLION, that sound like the $40,000 military hammer.

Yeah, the increase in electrical rates in California is the dirty little secret behind the State’s solar initiative. I have family in Oregon, Washington State, and Florida as well as friends in Texas. All have asked me to help them understand whether solar makes sense and at the rates most consumers pay for electricity (low to high single-digits of cents per kWh), it doesn’t.

In California, even our ‘ultra-low’ ‘deeply-discounted’ Uber-off-peak rated for charging EVs are essentially a hidden tax.

Charge your citizens an average of over 10 times what electricity is worth and suddenly the value of solar pencils out.

I was spending $700 for electricity before I installed my 4kW grid-tie system in 2016. After tax credits, that penciled out to a 10-year breakeven. Then literally a month after I got my system up and running, they changed the rules and decided a minimum ‘connection fee’ of $10/month could not be offset through production credits and my breakeven increased to 12 years.

Now with the TOU window changes coupled with ever-increasing rates, I had to pay $120 at True-Up (on top of my $10 minimum monthly) to pay for electricity for the first time in 5 years.

Next year it gets worse and in 2023 when they force us all onto the new ‘Peak Pricing 4pm to 9pm Every Day’ plan, it’ll get worse yet again.

I have no idea what my $700/per year tiered electrical bill from 2015 would have increased to by now if I’d never installed solar, but I suspect it would be at least double if not 258% as you say.

 

[shavermcspud]

Does anybody know if the popular Growatt and MPP "hybrid" inverters (or others) that have grid feedback have the ability to do BATTERY grid feedback?

Not sure where you are in the world bu EU kit for A/C coupled battery inverters do this.

 

[Hedges]

Water bill is what I'm feeling the pain of now, e.g. $360/month for latest 2-month bill.
During the water shortage, we were asked to reduce consumption, and they had to pay more for water the system bought.
Drought came to an end, and they said, "We don't want to lose the momentum we've gained ..." i.e., keep the prices high.
Then, fixed portion of bill was raised 30%. That after imposing rent control (to a much smaller percentage) on landlords who typically pay for tenant's water.
Water company itself is a private for-profit entity. But rates are set by the bureaucracy.
The reason for water conservation isn't to save water, it is to allow population growth, more subjects for them to rule.

With your new TOU window, consider adding panels aimed at afternoon sun, make some power after 4:00 PM when it is worth more.
Consider adding 3x the PV wattage aimed at morning sun.
If you have microinverters, not as easy to do this because they may already be over-paneled. With string inverters, easier to add a string of East or West facing panels.

Used to be $0.085/kW off-peak for me, now $0.15/kWh.