Storing Excess Energy

[Nomen Nescio]

If youre off the grid, I understand batteries are the usual way to store excess energy for use at night, but are there other ways to store it? For example, would lifting a heavy weight during the day, and letting it descend at night, coupled to a transmission and generator, be an alternative to batteries?

 

[Anthony Matonak]

If youre off the grid, I understand batteries are the usual way
to store excess energy for use at night, but are there other ways
to store it? For example, would lifting a heavy weight during the
day, and letting it descend at night, coupled to a transmission
and generator, be an alternative to batteries?

If you do the math you'll find that mechanical storage methods are
not as efficient or compact as batteries. In most cases they are
not as inexpensive as batteries either. This means that it is
possible to use some form of weights, water, springs, compressed
air, heat, ice or such things to store energy but the disadvantages
far outweigh the advantages.

Anthony

 

[News.bluewin]

If you do the math you'll find that mechanical storage methods are
not as efficient or compact as batteries. In most cases they are
not as inexpensive as batteries either. This means that it is
possible to use some form of weights, water, springs, compressed
air, heat, ice or such things to store energy but the disadvantages
far outweigh the advantages.

Anthony

Hmm, but the idea ist cool anyway.
Advantages:
Theoretically you dont't have any losses all day around because you can
easely lock it.
The sensitivy to temperature is also much smaller.
No lead-pollution.

Efficiency:
Efficiency of motor to tie the block upwards: 90%
Efficeny of gear : 75%
To release the energy : the same thing the other way round.
0.9*0.75*0.75*0.9 -> 45% efficency.

Hmm...How good are batteries?
Does anybody know?
Are there Websites about this?

Benni

 

[Anthony Matonak]

Hmm, but the idea ist cool anyway.

Rube Goldberg had a lot of cool ideas. That did not make them
practical.

Advantages:
Theoretically you dont't have any losses all day around because you can
easely lock it.

Storing energy by lifting weights may not involve ongoing losses
during the day but you'll have a lot of losses involved in the
storage and retrieval steps. This is not a new idea. It has been
discussed time and again on these newsgroups.

The sensitivy to temperature is also much smaller.
No lead-pollution.

Nickel-Hydride batteries don't have lead either.

Efficiency:
Efficiency of motor to tie the block upwards: 90%

I think you are being very optimistic here. Most electric
motors average around 60% to 75% efficiency. There are some
versions which can do better than 95% but they are very
expensive.

Efficeny of gear : 75%

You would likely require a lot of gearing. I'd be surprised
if you got 50% efficiency with the type of gearing required.
Remember, to store a typical house hold energy needs for a
single day you would have to lift something like several
railroad locomotives hundreds of feet into the air.

To release the energy : the same thing the other way round.
0.9*0.75*0.75*0.9 -> 45% efficency.

Hmm... 0.6*0.5*0.6*0.5 -> 9% efficiency.

Hmm...How good are batteries?

I'm told they run about 80% efficiency. That is, if you put
100 watt-hours in then you might expect 80 watt-hours out.

Does anybody know?
Are there Websites about this?

This has been discussed often and regularly. Try a google
search.

Anthony

 

[Steve Spence]

80% does not "far exceed", only somewhat exceeds, and is much less
convenient on a homeowner scale.

 

[daestrom]

The reason is that the electric utility business deals with trillions
of dollars every year (yes, really, trillions), and even just 0.1% of
a trillion is still one billion dollars.

Of course, not every utility deals in such huge numbers (these are
worldwide, and the US is "only" about 1/4 of the world's usage),
but even a "little" utility often moves tens of millions of dollars
in a month.

Ah true, true. We have a little fun in our plant because we calculate the
revenue generated by each revolution of the main generator. We use some
information from the plant-process computer to update it 'live'. Works out
to about $0.23 for every revolution of the shaft (as one put it, "a donut a
turn" ;-)

(This is perhaps *the* reason the efficiency improvements in
gas-fired generation a few decades ago were, and still are, such
a nightmare. Utilities build plants that are supposed to last 40
years, and are priced based on this. If repowering plants, or
adding building-at-a-time distributed cogeneration, can change
one's economics by a few billion, then it almost necessarily *must*
happen, yet to do so will wreck twenty or more years of planning.
Deregulation was and is an attempt to get "the market" to take over
the risks and rewards of changing generation technologies.)

And this is what all the 'stink' about 'stranded costs' has been with
forcing utilities to deregulate. They have Billions (with a 'B') of dollars
in investments they've made based on what the government agreed to and
*required* the utilities to do. Then the government just up and changes all
the rules and require the utility to sell the plants during a market glut.
Should the stockholders absorb the loss, the ratepayers, the government??
Decisions, decisions...

daestrom

 

[[email protected]]

What makes you think that anyone other than the Utility should absorb
the losses? Did anyone other than them take the profits? The billions
they invested did not come with a warranty from the government did they?
If they want the public to underwrite the risks then they should be
public owned not private.
Offgridman

 

[daestrom]

What makes you think that anyone other than the Utility should absorb
the losses? Did anyone other than them take the profits? The billions
they invested did not come with a warranty from the government did they?
If they want the public to underwrite the risks then they should be
public owned not private.
Offgridman

Lets see now, the PSC granted the utility a monopoly in providing electric
power, PROVIDED the utility agree to certain stipulations. One of those
stipulations is the utility *MUST* build plants of sufficient capacity to
supply future demands *as predicted* by the government, *not* the utilities
predictions. If they do *not* build for sufficient capacity to meet public
demand, the government would simply revoke their right to operate as a
utility in a service area.

So the government *forces* the utility to invest in plants and only allows
the utility to recover the cost over a 40-year amortization. Yes, FORCES
the utility to build them. And yes, they DID come with a warranty from the
government that they would be able to recover all 'just and prudent' charges
from the rate payers *and* make a small, fixed profit. These are agreements
that were in the rate-tariffs passed by a government body with the effect of
LAW.

The utility agreed to this because they were *guaranteed* a small, but
predictable profit. Remember how utilities were a bastion of conservative
investing? They would always pay their dividend to stockholders because
their profit was fixed by the PSC. Only gross mismanagement or costs that
were not 'just and prudent' would be disallowed from the rate base. In
fact, anyone selling electric power retail that was *not* under the control
of the PSC could be taken to court by the utility as infringing on their
'government-granted monopoly' (except for a few small NUG exceptions). That
is, the utility had an exclusive license by the government to sell retail to
the public.

But BANG, the government changes the rules. Yes, the utility was forced to
expand generation over the past 30 years, but we're sorry, you have to sell
that plant now at 'firesale' prices and you don't get to keep charging the
rate payers to pay back those bonds you wrote.

THAT is what stranded costs are all about. Government *forced* an
investment with *promise* that the costs could be recovered from the rate
payers in exchange for the right to operate a monopoly. Then the government
changed all the rules after they've made the investment so they cannot
recover the costs and others are allowed in to compete with the utility.

As far as saying the utility *should* have been a public government entity
and not a private company, that is mere speculation and *not* what
*actually* exists.


So the utility was forced to make an investment, the government forced the
utility to sell. Before, the utilities profit was limited by the government
and now the government is forcing utilities to sell off income-generating
assets at a loss.

If you were forced to sell your PV system at a loss and forced to buy power
from your competitor, simply by the stroke of the legislative pen, should
you absorb all those losses yourself??

daestrom

 

[Chris Torek]

What makes you think that anyone other than the Utility should absorb
the losses? Did anyone other than them take the profits? The billions
they invested did not come with a warranty from the government did they?

Actually, they *did*.

The Public Utilities Holding Company Act of 1935 ("PUHCA") established
a framework in which states (or other governmental bodies, but
generally states, as they were already doing this) would have all
kinds of control over electric utilities, and in return, the
utilities would get a *guaranteed* profit.

This is what made utilities perfect "widow and orphan" stocks: the
prices never really changed much, but the dividends were nicely
steady.

(PUHCA was required only because the utilities were escaping state
regulation by means of interstate commerce. Interestingly, during
the money crisis in late 1999/early 2000 in California that led to
blackouts, the Enrons of the electricity-trading world were once
again using interstate commerce as one of their tricks. I call
this the "money crisis" because the main problem was not a lack of
generation, but rather a lack of money to pay the inflated prices
to *use* that generation. Much of this traces back to price-fixing,
withholding, and general tightness in the natural gas market. When
some companies were claiming they *had* to charge $750/MWh just to
break even, not all of them were lying. This, by the way, is
$.75/kWh, more than 50% higher than unsubsidized PV electricity.
Solar PV is expensive, to be sure -- but occasionally it is actually
cheaper than "fossil-fuel" electricity.)

 

[daestrom]

That is just what is happening in Ontario. They deregulate and now we have a new
lind on our hydro bills.

Debt Retirement Charge. to pay for the debt incurred by Hydro before
deregulation. works out to be .7 cents a KWH with no end in site. After
de-regulation Hydro made a profit of 500 million in the first quarter and of
course it is not going to the debt.

How does the 500 million compare with past performance? Are you sure that
was 'profit' or was it 'sales' or 'revenues'? Quite a difference.

Here in the states, we've had some utilities 'write-off' their loss from the
forced, early sale of generation all at once. By reporting it all at once,
they move the debt/bonds they still have from one line of the balance sheet
to another. They still have to pay out the bonds with interest over the
next +20 years, but it won't be recorded as a 'debt'. So the money they
take in, to pay that bond is future 'profits'. But 'future' profits can
sometimes be less taxes if you have a lot of written off losses to carry
forward.

So the utility starts reporting larger profits (for the benefit of
shareholders), even though they still have this millstone around their neck
to pay off (bonds and long-term debts incurred to build plants).

Accountants and financial managers are *very* inventive.... But the bonds
are still getting paid, so I'm happy (I own a few).

daestrom