Comment by engendered | Hacker News Reader

Comment by engendered | Hacker News Reader

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>you can't even live 'off the grid' in a grid tied system

I can't find any references for your stated claim about Connecticut, however it seems deeply illogical given that a generator (which surely aren't banned), solar panels, wind, etc, all have the potential of feeding energy back to the grid in an outage. Which is why there are regulations and home inspections and all of that, to ensure that the appropriate safeties and switches are in place. Simply banning one of many possible mechanisms of generating power would be very short sighted.

Many regions that offer feed-in time-of-day tariffs are rightly trying to figure out how to accommodate battery systems, where some users are trying to game the system by charging a big battery array during low cost hours, and then "selling" it back to the grid during peak hours (at inflated, subsidized prices).

EDIT: As a reply to msandford, given that I can't reply lower -- the reason they have this limit is that the tariff price paid to home solar/wind generators is way above the bulk, "wholesale" price of power. It was created as an incentive to encourage green energy. So when you feed back their own power to them, it does them no favor given that now they're paying 2x+ what they would pay on the normal power market for power, and simply undermines the entire incentive program.

> where some users are trying to game the system by charging a big battery array during low cost hours, and then "selling" it back to the grid during peak hours (at inflated, subsidized prices).

The idea that a utility wants a heads-I-win-tails-you-lose kind of situation is annoying at best and downright infuriating at worst. If they're willing to sell power for $X now and willing to buy it later for $Y, what does it matter the method? I mean, there are people working on grid-scale storage batteries to do precisely that because utilities desperately NEED additional peak capacity when it's a hot day and everyone's A/C is on in the late afternoon. Why would it be OK for the UTILITY to utilize grid storage, but not an INDIVIDUAL?

http://en.wikipedia.org/wiki/Grid_energy_storage

  If they're willing to sell power for $X now and willing to buy 
  it later for $Y, what does it matter the method?

In the UK, to encourage adoption of residential solar panels there is a scheme of "feed in tariffs" where you can generate renewable energy and receive a guaranteed, above-market-rate price for it. The goal of this is to reduce carbon emissions.

For example, you can buy residential electricity for 15p/kWh [1] but sell energy from your small hydro installation for 19p/kWh [2].

Obviously, the goal of reducing carbon emissions would not be achieved if people simply charged batteries at 15p/kWh and sold it back at 19p/kWh!

Of course, this issue only arises because feed in tariffs are subsidised.

[1] https://www.gov.uk/government/uploads/system/uploads/attachm... [2] http://www.fitariffs.co.uk/eligible/levels/

Honestly, let them! They'll go bankrupt soon enough. And they'll achieve peak shaving in the process.

Lead acid batteries cost about $100/kWh of nameplate capacity, more like $200/kWh of usable storage. At a 50% depth of discharge you're going to get about 1000 cycles out of the battery.

http://www.mpoweruk.com/images/dod.gif

So assuming 100% charge, discharge, charger and inverter efficiency (reality is more like 60% through that whole cycle) a person stands to make about $0.06 per kWh per cycle (in the UK anyhow) and they can only get 1000 cycles.

$0.06 * 1000 = $60 per kWh per battery lifetime

That's only 1/3 of the cost of the batteries, completely neglecting the capital cost of the charger and inverter and the time spent to set the whole thing up. Further, once you take the realizable efficiencies into account, it's more like $40 not $60 so they're losing money even faster.

This is a problem that -- at least for now -- LITERALLY solves itself.

And they'll achieve peak shaving in the process.

Peak shaving is if you powered your own home off of your battery pack during peak times. The whole issue is that gamers -- who are essentially ruining "the commons" and pissing in the drinking well -- are instead abusing a system.

Again, no home battery pack is helping the power company. The rates are hugely subsidized to encourage green energy. The people who abuse it simply ruin it for everyone else.

You're right of course that it's not peak shaving, which is about shedding load. That was incorrect of me to state.

But it is peak generation, which is just as valuable.

> Again, no home battery pack is helping the power company.

Please re-read my comment where I detail the economics of pulling power off the grid at low price and selling it back at high price is actually net-negative for the individuals doing so. From this we can assume that it's net-positive for the utility company because they're basically getting "free money" from the people who aren't good enough at math to see that what they're doing is economically wasteful.

> The people who abuse it simply ruin it for everyone else.

The people who "abuse" it are paying $0.20/kWh of cost to make $0.06/kWh of revenue. That's REVENUE, not PROFIT. This is a losing strategy, it loses $0.14/kWh, at least according to the math I did.

It's entirely possible that my analysis is wrong for some reason, but rather than just stating "they're ruining it for everyone!" maybe you could rebut my reasoning or something? Just stating something as a fact doesn't make it so.

It isn't just as valuable. Again, the wholesale market rate is significantly less than the subsidized tariff that they pay homeowners to feed back.

To your final paragraph -- you essentially made up numbers and then demand that I refute them. 10. 14. 1.3e12. Refute that.

The single and only reason this side discussion even happened is that I noted that some power companies will refuse to allow grid feed-in if you install battery packs, for the reason I noted.

Did you even re-read what I wrote?

Lead acid batteries cost about $100/kWh nameplate. But at 100% depth of discharge they wear out VERY quickly. We'll assume 50%. That means they cost $200/kWh in actual capacity.

At 50% depth of discharge a lead acid battery will only get about 1000 cycles before it's not very useful anymore and needs to be replaced.

$200 / 1000 cycles = $0.20 per kWh per cycle.

That's the fixed cost of a lead acid battery. Every time you charge and discharge it, you've lost $0.20 per kWh in terms of the capital cost of the battery. This has nothing to do with the price of power, but it has to do with the depreciation of the asset.

Okay so now let's deal with power cost. It's 14p to buy low, 19p to sell high. Since I'm in the US I'm going to convert that to dollars at the rate of about 1.5 which means that the MOST money you can hope to make on the arbitrage of low price to high price is $0.06

Now let us compare $0.20 per cycle of cost with $0.06 per cycle of revenue (again ignoring the fact that in reality nothing is 100% efficient) and we can easily see that this is a losing proposition. It'll lose AT LEAST $0.14 per kWh per cycle for the person trying to operate this arbitrage scheme as a business and they'll soon go bankrupt. Problem solved.

Now if the cheap power was $0.01 and the expensive power was $0.50 then they might be able to make money. But from what I understand of the power pricing, that's not the case.

If you'd like to continue to argue, please do so with actual numbers that mean something and/or are based on reality, rather than belligerent trolling. Please see this link where I previously did the analysis that you couldn't be bothered to read: https://news.ycombinator.com/item?id=9063702

Belligerent trolling? How utterly obnoxious.

You are inventing numbers from fantasy, and demanding retorts. What an astonishing bore, your inconsistent, incoherent point not in the least viable. Find a hobby.

Peak generation... are you referring to Tea Time?

https://www.youtube.com/watch?v=UTM2Ck6XWHg

The idea that some people fetishize disruption and heads-you-loose, tails-I-win situations baffles me. The utility has expenses beyond the cost of power generation. They don't exist to provide a subsidy to cool upstarts. They provide critical infrastructure for those cool upstarts and everyone else.

There are certainly a lot of perverse incentives and inefficiencies in the current model. Even so, its either ignorant, childish, or intellectually dishonest to act like it is outrageous that a utility has a simplified pricing model that doesn't accommodate the outliers among the outliers (residential customers with large solar and battery installations), or that their overall pricing allows margin for cost recovery and profit on power they deliver, whatever the source.

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