Energy Supply
Steffen Huber (91) 1953 posts |
Not sure about “how much heat”, but the problem for using such heat is usually that the highest temperature available is south of 90 degrees Celcius, which immediately invokes good old Carnot who tells you “this is getting expensive if you want to produce electricity from it”. Normal boiling water-based power stations start from a temperature between 350 °C and 650 °C – the higher, the better. For safety reasons, nuclear power usually uses the lower end of this temperature range, and it does not really matter too much, because the power source is extremely cheap.
Electrical power distribution is not really the problem. Even with not-so-fancy high voltage distribution (380 kV), the grid usually loses only around 8% of power, and most of the loss is at the last few kilometers. The problem is almost never having a source of energy. Our sun is a very powerful source of energy. The problem is always to make use of this energy – sometimes, it is just too expensive. In Germany, you can witness the results of the extremely expensive “Energiewende” – a lot of money spent into transforming electrical energy production from coal/lignite and nuclear power to wind, sun and biomass. Insane amounts of money spent, but the results are very thin on the ground. Instead, the government has to order utility companies to keep conventional power sources online (despite being no longer economical) to keep the grid stable. We have now so much photovoltaics and wind power generation that, if both run on full load, much more than 100% of Germany’s electricity consumption is met. As this is independent of demand, you either have to sell surplus power for extremely cheap prices (sometimes even paying someone to “buy” it – a sure way to keep our southern neighbours happy when getting paid to fill their pumped storage), or you have to throw away possible power generation. But some of the time, wind and photovoltaics don’t even manage to provide 1% of the electricity consumption. It’s a nightmare for grid stability. A better name for the “Renewables” would be “Unreliables”. |
Steffen Huber (91) 1953 posts |
This is only correct for conventional electrical heating. You can alternatively drive heat pumps with this electricity. This might give you up to 50kW of heat, because you can use additional heat from the environment (air or water). Air source heat pumps usually give you a COP of 2.5 to 3 overall, while Ground-source heat pumps can peak at a COP of around 5 and give you an average of 4 through the year. However, heat pumps only give good efficiency if you have the right heating system which operates on low temperature. If it needs more than 45 °C supply temperature (or is “inlet temperature” the right wording?), the achievable COP goes down rapidly. So depending on a lot of circumstances, using electricity for heat production (e.g. if your electricity comes from a gas-fired combined-cycle gas-and-steam turbine power plant with an efficiency of more than 50%) might be a lot more efficient than using a gas-fired boiler in your home. If you take emissions of air pollutants in account (which can be managed much more efficiently when having a big central power plant), it gets even more complicated. |
Steve Pampling (1551) 8172 posts |
Basically, what you’re saying is “insufficient storage built into the project specification”. |
Rick Murray (539) 13850 posts |
France is filling up with those wind generators. I think they said that they provide about 11% of the grid power. You’re always going to need traditional power stations, with the green stuff helping to take some of the load. What you aren’t going to do is replace one with the other. Not unless you’re happy to turn your country into a technological wasteland on the days when the wind doesn’t blow (and nights when the sun isn’t shining…).
Isn’t this basically the result of some hamfisted approach to meeting arbitrary emissions targets? Less coal means less CO2 means “we saved the Earth” or something. Because spaffing huge amounts of cash on wind turbines is quite a bit cheaper than relocating those major cities that happen to be either on the coast or on rivers at or near sea level.
I think France’s main concern with nuclear power isn’t so much the inherent risks or the nuclear waste, but rather the likely effects of having some terrorist nutter getting in and being able to blow up enough to cause a major problem. |
Steffen Huber (91) 1953 posts |
Yes, but knowingly so. Because storage for the capacity needed is very very expensive. You need seasonal storage if you want inherent grid stability. There is a great back-of-the-envelope calculation to visualize the necessary dimension: if wind and photovoltaics are providing 50% of your grid power on average, and you want to store enough electrical energy for a two-week outage of these providers, you basically need to pump the whole water of Lake Constance to the height of the “Zugspitze”, the highest mountain in Germany (nearly 3000m). Basically, pumped storage is not possible for the power capacity you will need. And the alternatives are either expensive or inefficient – or both. One storage approach is to produce methane from air CO2 (which has the immense benefit in the case of Germany that you have basically unlimited storage for methane already). Best case is 25% efficiency. So you need around 300% installed capacity of EE power supply that you can average out a year’s supply. As I said – insane. There is already a “field study” being done in reality – they tried to go 100% renewable on El Hierro, a small Canary island (i.e. optimal conditions for both wind and photovoltaics and pumped storage, and no big consumers like industry). Guess what they needed to use for backup power for most of the year…and guess the cost… |
Clive Semmens (2335) 3276 posts |
For an understanding of while nuclear wonks hate renewables so much, see http://clive.semmens.org.uk/Energy/CapFacI.html |
Clive Semmens (2335) 3276 posts |
As for pumped storage on El Hierro – putting a large reservoir up a mountain on a seismically active island isn’t a terribly good idea. Folks in Chamoli in India could have done with that bit of advice, see today’s news. There are other methods of energy storage, but the capital costs are currently high compared with fossil fuel plant. |
Steve Pampling (1551) 8172 posts |
The UK is a bit short of mountains but in certain cases there is enough elevation for hydroelectric pumped storage |
Clive Semmens (2335) 3276 posts |
Yup. There’s just over 30 GWh of pumped storage in the UK at the moment, and it’s reckoned that there could be about 500 GWh worth, although there’d be quite a bit of objection to a lot of the potential sites. See http://clive.semmens.org.uk/Energy/EnergyStorage/PumpedHydro.html |
Colin Ferris (399) 1818 posts |
UK has been getting electric power from France for sometime via undersea cables – High Voltage DC (I think) Talk about laying electric cable from Iceland to UK – using volcanic heat for power. Liquid Air for electric storage. Using compressed Air for small cars/motorcycles has been tried. |
Stuart Swales (1481) 351 posts |
I think that they acknowledged that Glen Doe would probably be the last such acceptable scheme. |
Clive Semmens (2335) 3276 posts |
Yup – but this isn’t when we can’t generate enough ourselves, it’s when France’s demand is low, and rather than shut down their nuclear power stations they’d rather sell electricity at below the cost of gas for our own gas turbines. It’s to do with the marginal costs: nuclear power is expensive, but it’s mostly in the capital charges, not the variable costs. When demand is high in France, we sell them power – even though demand is often high in the UK at the same time.
Yes, although that could possibly change as the situation changes. But there are other technologies coming along – and it’s not batteries! |
Chris Hall (132) 3558 posts |
Yup – but this isn’t when we can’t generate enough ourselves, it’s when France’s demand is low, and rather than shut down their nuclear power stations they’d rather sell electricity at below the cost of gas for our own gas turbines. It’s to do with the marginal costs: nuclear power is expensive, but it’s mostly in the capital charges, not the variable costs. It is important to realise that electricity cannot easily be stored (pumped storage at Dinorwig was intended to be there to cover transients but was taken over by the accountants to pump money); that nuclear power stations cannot work well except at steady output; that links across the channel are of limited capacity and run at DC with convertor stations each end so that the turbines in England and France do not have to turn at the same speed (and for other more complicated reasons). Excess nuclear power is thus cheap and there are lots of them on the north coast of France to take advantage of the prevailing wind (just kidding). The trouble is if you attempt to scale this up to Grid levels of production, where are you going to store that kind of power in a cost effective way? In a purpose-built facility in Wales at a location whose spelling and pronunciation changes depending on the context. Somewhere near Manchester was also mooted amidst great secrecy as such installations generally flood a large area. I still think the future is in small scale power generation, without the expensive grid power. Ah – we did try that and found it was cheaper to built huge electricity distribution networks as the local power undertakings all carried spare capacity that was of use only to their local area. So it is the past (pre 1930s I think) of which you are dreaming. In 1925 Lord Weir chaired a committee that proposed the development of the Central Electricity Board (CEB), which would connect the most efficient power stations in Britain. This link would be established with a ‘national gridiron’. Various names were tried over the years including CEA (Central Electricty Auhtority) and then BEA (British Electricity Authority) This seemed to clash and it proved difficult to decide who carried the more passengers and British Eurpean Airways narrowly won this battle and the CEGB was born in England (Wales was part of England then and some say Monmouthshire still is). Scotland did something similar but different of course – a better idea with generation and distribution merged. In England distribution was split into 275kV (from 1950)/400kV (from 1965) and strategic parts of the older 132kV network going to CEGB with lower voltage distribution going to the area boards which dealt with the great unwashed. The accountants messed all that up in privatisation. In 1926 the proposals were accepted and became recognised laws. The National Grid was born in 1935 with seven grid control rooms in locations that were deliberately kept vague. It was completed in 1936, on time and the areas were connected by the engineers on their own initiative (engineers were in charge then, not accountants). It worked. Spare capacity (which was sorely needed) could now be shared. |
Steve Pampling (1551) 8172 posts |
Dunno, has anyone tried water electrolysis? |
Chris Hall (132) 3558 posts |
I don’t think I would like to live near a bulk hydrogen store … |
Steve Pampling (1551) 8172 posts |
1960s – One set of relatives lived in Attercliffe and couldn’t get a TV signal when the gas holder was low. Down the hill1 there were houses directly across the road from the storage. Of course the storage doesn’t have to be close to any habitation. Underground storage near a wind turbine perhaps? Or maybe in the grounds of a repurposed/refurbished power station? 1 In Sheffield the hills are proper hills. The sort of location where 2-up and 1-down describes the number of floors other than the one on street level (at one side) and takes no note of cellars. |
Rick Murray (539) 13850 posts |
That’s a conservative estimate. You need to go through a mile or two of woodland, expect to tack an extra zero onto the end if there aren’t subsidies available. Many utilities will hook you up for free of you’re less than about 100 feet from a utility pole (their expected income will outweigh the costs), otherwise a guide price is about $25 per foot for simple flat land. Add complications (like trees) and the price shoots up.
I think that depends upon where you are. In the very southern states (say, Arizona), there is something of a war beginning because lithium batteries have matured to the stage where, when hooked to large solar cells, they can almost replace reasonable domestic electricity use. I think the utility companies will need to rethink their business plans because I can imagine by the end of the decade, personal electricity generation will will have progressed to the point to render a mains connection unnecessary. However, somewhere grey and cold like Maine (Britain, northern France…), where you typically need more power at a time when the sun doesn’t shine much, the mains grid will be necessary for the foreseeable future. |
Rick Murray (539) 13850 posts |
When mom first bought this house, three phase was provided by stringing out four bare conductors from a nearby farm. It was functional, but not terribly good. The power floated at around 220V, but dipped towards 190V when I put the kettle on. Three years ago, our supply was rerouted up the driveway (a half kilometre) with seven or eight new poles and twisted isolated cable. https://heyrick.eu/blog/index.php?diary=20180211 Now the supply is steady and constant. Luckily it didn’t cost us a thing as the mass rewiring project is part of the push to get everybody onto a smart meter, so it’s the government picking up the tab for all of this. |
Alan Adams (2486) 1149 posts |
I used to work at a rural site which had an overhead 3-phase supply, I think at 2KV. One day we had a lightning strike on one of the poles, and one phase dropped out. This got interesting very quickly. With 3-phase, the neutral is derived as the “average” of the three phases. With one phase missing, the neutral went to about 80 volts above earth. As a result the two existing phases were operating at around 180 volts, and the third at about 330 volts. Lost of blown light bulbs, various desktop systems failing. Shortly afterwards someone was despatched to RS components in Corby with an order for a large assortment of contactors to replace those that had welded shut or burnt out. Very fortunately the computer room was fed by an online UPS, meaning the batteries were on continuous charge, and the inverter generated 240 volts AC from the batteries to supply the computers. As a result the room power was initially unaffected. The charging side shut down immediately, so we just had time to shut things down before the UPS stopped supplying power, but at least we had no damage. The backup generator hadn’t kicked in, because the phase it checked for incoming power was still running. It didn’t matter – the air conditioning was not on backup power, so we only had 15 minutes before everything would have overheated anyway. |
Rick Murray (539) 13850 posts |
Luckily mine went the other way. https://heyrick.eu/blog/index.php?diary=20160810 |
Steve Pampling (1551) 8172 posts |
The southern states really ought to be investing in large solar generation/storage installations to sell the power to more northerly states without the sun rich generation capability. |
Steffen Huber (91) 1953 posts |
That entirely depends on the size of the storage you need. I would be interested in a rough calculation here. You’d need seasonal storage, which makes it very expensive. If your consumption is beyond a few kWh per week of course. Of course you can cheat and use a diesel generator for backup, like most off-grid solutions do. |
Rick Murray (539) 13850 posts |
Yes, you are. You live in a place where 43C is a normal summer temperature, oil is cheap, and the previous administration didn’t give a flying flamingo about the environment. I live in a place where a run of days over 30C is a heatwave (panic! panic!), where oil is expensive, and because of the environment it’s getting less and less attractive to use wood burners (people adopted them in place of the dead dinosaur liquid, but ended up with trees being burnt faster than they could grow). That’s not to say that it’s all electric, but there is a lot of electric heating. Those heat exchanger gizomos are getting quite popular. BTW – I’m lying wrapped in an electric blanket and it’s |
Chris Hall (132) 3558 posts |
I think our domestic electricity prices in GB are probably higher than yours in North America – ours are $230/MWh and $130/MWh (converted to dollars) with the cheaper price for overnight electricity for storage heaters, it being easier to store heat than electricity. Our peak consumption is for heating in winter. |
Chris Hall (132) 3558 posts |
There is nowhere to put the large water tanks. I assume they are too large to go in the airing cupboard? |