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PostPosted: Dec 28, 2015 5:18 am 
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E Ireland wrote:
alexterrell wrote:
You don't have to go off grid. But to cut your imports by 99%, in somewhere like Arizona, you'd need somewhere between 10 and 20 KWh of storage. That's not overly expensive.


Even 1% imports will cost something like 30-40% as much as 100% imports.
You will hit hard grid cost limits before then.


1% import cost is limited by the cost of a local grid and diesel generation, which can be provided at £18/KW per year. A typical house in "dry tropics" with 5KW of solar panel, and 10-20KWh of storage, might need a 1KW back up generator, used once every two years or so.

Of course, if that can be shared over a grid, a more efficient solution can be provided. (A 1KW generator can't be provided for £18 per year). The grid is also very valuable for export, as solar panels need to be oversized. Of course, that creates the problem of what to do with the surplus over the entire summer, which is why solar doesn't work for Germany or the UK.


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PostPosted: Dec 28, 2015 5:28 am 
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Striking a balance .....

I was talking to a backer of molten salt reactors - hence a biased anti PWR/BWR bias - about France's decision to reduce nuclear power to 50%.

My view was this is a crazy decision. But, given that
- The EPR can only deliver electricity for £92.50,
- Onshore wind farms can deliver for £80
- France has lots of empty windy coast for wind farms (unlike the UK, where it's all protected)
- France has a reasonable amount of hydro, and nuclear can somewhat load follow

A 50% nuclear, 40% wind (and a touch of solar), 10% hydro solution will be cheaper than a 90% Gen III nuclear, 10% hydro solution.

Not many people are seriously suggesting a 100% nuclear Gen III grid these days - in any large country - it will be suboptimal. Even if AP1000s deliver at £70/MWh, a mix of nuclear, renewables, and a splash of gas, will be cheaper, especially in "dry tropics" where solar is so cheap.

If we can get MSRs selling at £30/MWh, then 100% nuclear makes sense for northern countries, and a solar/nuclear mix for tropical countries.


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PostPosted: Dec 28, 2015 8:55 am 
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The problem with wind in the UK is it has essentially zero guaranteed generation.

January/February 2010 - country had arctic weather with giant static fogbanks covering most of the country.
Wind power production was single digit percent of nameplate - in other words it was almost zero.

In this glorious capacity-guaranteed future where we are using diesel generators we would have burned an awful lot of diesel.

Nuclear with some CCGTs and Option Tempo esque load shifting is probably the best bet in the UK to be honest.
Nuclear park to something like 100GWe.


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PostPosted: Dec 28, 2015 12:26 pm 
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Quote:
about France's decision to reduce nuclear power to 50%


Given the current economical situation in France I don't think that will happen. The most probable scenario is that the lifetime of the current fleet will be extended to 60 years. It is the easiest and the cheapest solution (except if MSRs arrive soon and are really inexpensive).

I also think that the current EPR will not be built in many numbers in France (maybe just one unit : the unit in Flamanville). They are preparing a simplified EPR with more emphasis on economics.

Quote:
Not many people are seriously suggesting a 100% nuclear Gen III grid these days - in any large country - it will be suboptimal.


The cost of Gen III reactors will considerably drop if they are built in massive numbers.


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PostPosted: Dec 28, 2015 1:26 pm 
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macpacheco wrote:
The building I live on (upper middle class 5 stories) consumes about 20000kWh/yr. Not far from a single average USA household.
We need about 10% of our roof space to do solar (even with current 18% efficient panels).
A building 3x higher can still do it with surplus space.


Only if you seriously reduce energy consumption compared to current levels in the first world.
Which would imply a drastic reduction in standard of living.

Really we have to calculate for an increase in electricity consumption.
Even 200MWh/yr as you propose for the roof would only be able to handle a dozen apartments at most, and would require an enormous power storage system.


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PostPosted: Dec 29, 2015 12:29 am 
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E Ireland wrote:
Titanium48 wrote:
Solar can't be a big part of the total production capacity at high latitudes, but it could make a valuable contribution to AC peak shaving, at the precise time when higher than normal temperatures are limiting the capacity of transmission lines and thermal generating stations (including nuclear).


Except at higher latitudes AC peak shaving is worthless.
Peak demand in the UK occurs in January or February at roughly 6pm. In the dark.
The situation is similar in most of Europe.

Same here in Canada, but when it is cold out you have extra heat sink to boost the capacity and efficiency of any sort of thermal powerplant, and you can feed more power through your transmission lines without overheating them.

E Ireland wrote:
Titanium48 wrote:
Maintaining one grid would be cheaper than two, but you are taking a big efficiency hit, even with 61% CCGTs. Until nuclear can take over from gas completely

Efficiency means little - I was talking about the total cost of the solution.
SUre we would burn more gas but savings in maintenance of two grids and two sets of billing infrastructure and alll that would overwhelm the increased raw material costs of just burning the gas.

You are assuming the price of gas will remain low. It may not. Carbon taxes and opposition to shale fracking are real threats to cheap gas
E Ireland wrote:
Titanium48 wrote:
the most efficient way to use gas would be small scale combined heat and power in every house.
Peak heat demand times match up well with peak electricity demand, and the winter heating peak is complementary to the summer solar peak. Distributed generation would also enable increased urban densities without grid upgrades (which might be relatively inexpensive, but definitely not free)


Actually it isn't.
100 energy units of gas in a CHP plant produces something like 30 units of electricity (assuming you actually need this much which you normally will not) and 65-70 units of useable heat.
Even assuming that you want heat in those proportions you can do much better.

100 energy units of gas makes 60 units of electricity in a CCGT plant.
30 units of electricity is supplied as electricity and 30 units is used for the houses heat pump capability.
The majority of heating demand in many latitudes is direct space heating - air to air heat pumps can obtain COPs as high as 5:1
Which means I have provided 30 units of electricity and 150 units of heat from that 100 units of gas.
And energy demand changes between electricity and gas can be easily be altered without reducing total system efficiency.
A CHP plant can't hope to match that.

An air source heat pump COP of 5? Maybe at well above freezing outdoor temperatures where you hardly need any heat anyways. Not at -20 C. You will be lucky to get a COP of 2 then. You do have a point with a ground source heat pump hough. A COP above 3 should be possible with a near freezing source, plus you get essentially free summer A/C - just pump the glycol through a fancoil unit.


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PostPosted: Dec 29, 2015 5:39 am 
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Maritime climate remember. In the UK Sub freezing temperatures at rather rare. Never known it to get below -10C


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PostPosted: Dec 29, 2015 6:54 am 
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Titanium48 wrote:

macpacheco wrote:
the most efficient way to use gas would be small scale combined heat and power in every house.
Peak heat demand times match up well with peak electricity demand, and the winter heating peak is complementary to the summer solar peak. Distributed generation would also enable increased urban densities without grid upgrades (which might be relatively inexpensive, but definitely not free)


Actually it isn't.
100 energy units of gas in a CHP plant produces something like 30 units of electricity (assuming you actually need this much which you normally will not) and 65-70 units of useable heat.
Even assuming that you want heat in those proportions you can do much better.

100 energy units of gas makes 60 units of electricity in a CCGT plant.
30 units of electricity is supplied as electricity and 30 units is used for the houses heat pump capability.
The majority of heating demand in many latitudes is direct space heating - air to air heat pumps can obtain COPs as high as 5:1
Which means I have provided 30 units of electricity and 150 units of heat from that 100 units of gas.
And energy demand changes between electricity and gas can be easily be altered without reducing total system efficiency.
A CHP plant can't hope to match that.

macpacheco was almost correct. The most efficient way to use gas is in a domestic scale fuel cell - such as Bluegen's - at 60% efficiency. If you want you can use the electricity in a heat pump, and can even use the 40% loss to preheat external air to increase the COP.

That would have been a wonderful way to balance renewables. The fuel cells would mainly run in winter, providing efficient heating, but could also be called upon to make up short falls in summer (when they'd dump the heat).

A couple of problems:
1 The fuel cells are expensive
2 They use gas
3 As a result of (1), Ceramic Fuel Cells went into administration

The "green" movement never got behind the technology, preferring instead to have diesel generators backing up the wind turbines.


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PostPosted: Dec 29, 2015 8:25 am 
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alexterrell wrote:
Titanium48 wrote:

macpacheco wrote:
the most efficient way to use gas would be small scale combined heat and power in every house.
Peak heat demand times match up well with peak electricity demand, and the winter heating peak is complementary to the summer solar peak. Distributed generation would also enable increased urban densities without grid upgrades (which might be relatively inexpensive, but definitely not free)


Actually it isn't.
100 energy units of gas in a CHP plant produces something like 30 units of electricity (assuming you actually need this much which you normally will not) and 65-70 units of useable heat.
Even assuming that you want heat in those proportions you can do much better.

100 energy units of gas makes 60 units of electricity in a CCGT plant.
30 units of electricity is supplied as electricity and 30 units is used for the houses heat pump capability.
The majority of heating demand in many latitudes is direct space heating - air to air heat pumps can obtain COPs as high as 5:1
Which means I have provided 30 units of electricity and 150 units of heat from that 100 units of gas.
And energy demand changes between electricity and gas can be easily be altered without reducing total system efficiency.
A CHP plant can't hope to match that.

macpacheco was almost correct. The most efficient way to use gas is in a domestic scale fuel cell - such as Bluegen's - at 60% efficiency. If you want you can use the electricity in a heat pump, and can even use the 40% loss to preheat external air to increase the COP.

That would have been a wonderful way to balance renewables. The fuel cells would mainly run in winter, providing efficient heating, but could also be called upon to make up short falls in summer (when they'd dump the heat).

A couple of problems:
1 The fuel cells are expensive
2 They use gas
3 As a result of (1), Ceramic Fuel Cells went into administration


Whilst they are sixty percent efficient - they cost such an enormous amount of money that they are not really very viable.
CHP plants are expensive enough as it is that combining one with a heat pump will end up enormously expensive.
You also lose access to diversity - what is the part load efficiency of the fuel cell?


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PostPosted: Dec 29, 2015 10:42 am 
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To work there would need to be some technical development and volume driven cost reductions - as has happened with solar cells. Also, they don't cycle well, so would need to be coupled to a battery.

I think they were the technology of the future :)


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PostPosted: Jan 05, 2016 9:38 am 
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I think all available energy sources should be used in the niche where they are most suitable and technology has to be developed to match.
Wind should be used to store compressed air in the tall towers required for it and used dispersed near points of use. Wind farms should be avoided. It is best used for climate control with heat pumping, water pumping and mechanical work at home and farm. It can be converted to electricity but may not be economical.
Solar is best stored in battery and used for lighting and electronics.
Gas is best used for heating and cooking and industrial heat.
Heavy industrial power demand and the grids should move from coal to nuclear.
Liquid fuels are unavoidable for transport including air transport.


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PostPosted: May 01, 2016 1:30 pm 
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https://en.wikipedia.org/wiki/Wind_power_by_country
There is much more wind power installed in the world but a search for wind power in the forum pointed to solar power threads. I guess that wind is too down-market.
The more I think about wind-power, the more I like more basic and lower cost technology. The wind power can have a good niche in distributed power generation. It could be made lower cost up to storage level by producing and storing compressed air in the wind towers. If close to points of use, the compressed air could be economically used for
a. All mechanical work.
b. Water pumping.
c. Air conditioning using heat pumping.
Compressed air can be used to run a turbine for electricity but a better alternative may present itself. The storage towers would be thicker and could be used for mounting solar panels on sunny side and batteries on shady side for electronic (TV, telephone, internet) and lighting use. The cost of compressed air storage could save much more in low use generation and transmission.


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PostPosted: May 02, 2016 12:23 pm 
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Quote:
You also lose access to diversity - what is the part load efficiency of the fuel cell?


This should be quite good, or at least can be made to be good. The cells are modular so you can do things like run x number at full power and shut off the others. AFAIU it is one of the key reasons for fuel cell vehicles being more efficient - good part load efficiency.


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PostPosted: May 02, 2016 1:59 pm 
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It has happened many times before. Self deception and wishing for things, no matter how sincerely, do not overcome realities.

I guess I do not quite understand the continued deception from the renewable side of things. Solar is especially bad now that wind is such a known financial and objectionable energy source. I read serious studies such as the Brooking's Institute paper on energy choices (including all currently known choices and their costs and environmental impacts) with clear analysis of costs, capacity factors, and avoided CO2 emissions and the conclusions are that we would be better off 50 years from now, with lower CO2 emissions, if we had NO solar power plants at all. But, if we continue to push solar, our poor and weaker class and undeveloped countries would be worse off financially, and our CO2 situation worse as well -- even with a carbon tax.

Then there is the Google study from IEEE... clearly pro solar Stanford trained Ph.Ds. sadly had to conclude they were wrong about solar and it cannot meet the CO2 objectives ahead. They conclude we need new breakthrough technology.

No matter the studies, there are still self-interested parties pushing to force renewables when serious studies show the illogic of it all. Maybe a thousand years from now, but they are not the answer currently.

One can wish renewables did not have intermittencies and fall short by a couple of million eVs per unit atom, but as they say, if wishes were horses.... As a life long environmentalist, I wish solar was a better choice, but I cannot rationalize that idea myself, given the data. Maybe I need a vested interest reason to change my mind.


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PostPosted: May 02, 2016 2:04 pm 
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A renewable world might be plausible at not world ending cost if a global power grid could be constructed, although that would require voltages far above what are currently practical (~1200kVac and 1100kVdc).

After all you could build a giant saltwater lagoon in Chile within a couple of miles of the shore, but 600m above sea level.
That could store terrawatt-hours of energy.


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