Nick's Comments

Re. Anonymous comment #9

I must admit I hadn't checked out Iceland's renewable resources, (my calculations were based on the figure for the amount of copper that was to be used in the cable and whether it was justified) but having now done so they may be looking to capitalise on these resources, including hydro power. Apparently Iceland has about 50 TWh per year (~5.7GW average power) of currently untapped combined geothermal and hydro resources much of which I'm sure they would be happy to export if possible. Based on this 5GW is probably an upper limit, allowing for the fact that they are not fully RE sourced themselves yet and that a 5GW connector would be the peak rating, the average would be somewhat less.

Regarding your point of whether the UK would want to be a long term importer of electricity I am sure the government would prefer not to be but I suspect that we won't have much choice; I think it highly unlikely that we can meet our energy needs, even just electricity, from indigenous RE resources and it probably makes more sense to buy renewable electricity than to buy fossil gas to to generate it our selves. Also considering the possibility of transport, particularly private, moving towards electric vehicles (and I suspect it will, a recent UK report says that 60% of new vehicles sold in 2030 will be EVs), I think it would be much better to import 1KWh of cheap renewable electricity from Iceland than about 4KWh of oil/petrol from the Middle East or elsewhere.

Bob M

This connector will have to be HVDC, at a guess somewhere between 200KV & 500KV and never mind the MW, at this distance I suspect that its capacity will be several GW to make it viable, possibly 5GW upwards.

A transmission line of this capacity and length would probably have a current density of between 0.5 and 1.0 Amps/sq-mm in order to keep losses and Joule heating to acceptable levels. Taking a 5GW capacity, mid current density value of 0.75 Amps/sq-mm at say 200KV then peak current is 25KA (5GW/200KV) requiring cable diameter of 33,333 sq-mm (25KA/0.75A per mm sq) or 333sq-cm. Two cables are required so total cross-sectional area of 667 sq-cm requiring 593Kg/m (593t/Km) of copper, not too far off the 800t/Km. A quick scan of the net suggests that the voltage may to be lower than 200KV, at 150KV (Borealis Group DC-cables max rating) weight would be 791tonnes/Km!. This calculation is however a guestimate, if the transmission voltage is much higher and the power is somewhat less than 5GW then this figure could be out by a factor of 10, i.e. should be 80t/km, still quite a lot though.

Regarding costs, I think you will find Bob that $3.75 is the price per pound (lb) or $8.25Kg, this correlates to about £4,125M/Km ($6.6M.Km). However the BritNed link was 450KV and 1GW which this copper price would require about £400K/Km of copper, about 20% of the cost of the installation.

A better answer would be to find a way to manufacture the recently discovered material graphene in bulk and cheaply. With a higher conductivity than copper, probably about 10% of the weight and an almost unlimited supply of raw material, carbon, it would be a much better solution.

Cliff:
You're right of course and I do appreciate that baseload and renewable backup are quite different, I was considering backup from the overnight perspective when the sun goes down rather than peaking response, OTEC themselves I believe are pushing the baseload angle. There's a free webinar here on OTEC and others on lots of other green technologies.

Richard, Re: 'the heat source is from the earth itself'
With HVAC ground source (GS) heat pumps the heat comes initially from the Sun by heating the ground, this is not to be confused with geothermal (GT) in which the heat is generated within the ground from such mechanisms as radioactive decay or from the Earth's core. Generally GT requires much deeper heat collectors than GS except where the Earth's crust is thin such as in Iceland.

Anonymous:
I would think the risk of catastrophic failure of one of these plants is likely to be very low if they are designed correctly, considering all the modern safety requirements. However, ammonia is very soluble in water so I would expect that the predominant risk is likely to be from leaks; due to failure of seals, valves or container fractures, causing water contamination which is still likely to be pretty serious, although catastrophes probably can?t be ruled out 100%.

The selling point with OTEC is that it provides base load and backup for intermittent PV and Wind. However this may not be such a big plus as I believe EOS have now started shipping their Zn-Air rechargeable battery technology which, at their stated cost of $160/KWh and a life of 30yrs & 10,000 full cycles works out at only about 1.6¢ per KWh over the life of the cells.
If this is used in conjunction with Green and Gold's SunCube CPV product, producing electricity for a claimed 6.0-8.5¢ (Aus)/KWh (in Australia), then total cost is less than 10¢ per KWh. If land is in short supply on some small Caribbean or Hawaiian islands why not offshore the PV! too!

'But despite the fact that the idea for the technology is more than a century old; to date, OTEC has only been successfully demonstrated on small scales of less than a quarter of a megawatt (MW) and has yet to produce utility-scale power.'

This may not be a bad thing.

OTEC performance is limited by its Carnot efficiency which means that at these temperature differences the efficiency is only a few percent, probably less than 4%. The main action of this technology is therefore to transfer 95% plus of the heat energy from the surface waters to the deep ocean water, a 1MW output plant would transfer about 19MW+ of power from the surface to the deep ocean. At a utility scale implementation of 100's of MW I would suspect that this level of heat transfer could have massive local, and possibly wider, ecological effects, possibly affecting ocean currents, at least at the local level.

To me this scheme has similarities to ground source heat pumps which rely on the sun heating the ground in the summer which acts as a heat store for extraction in the winter. The amount of heat supplied by the sun doesn’t increase when heat pumps are installed so there has to be a net reduction in ground temperature where they are installed, which in the worst situations causes the ground to freeze and stops the pump from working. By analogy the oceans will not absorb any more solar energy to compensate for the energy extracted but the act of extracting energy is achieved by transferring heat from the surface to the deep ocean. My concern is that this could have substantial environmental impacts if implemented at large scale, the Gulf Stream is already slowing, it doesn’t need any more help.

Before OTEC 'goes large' I think there probably needs to be some serious verified modelling of its environmental affects if implemented at full utility scale because I'm not convinced these will be a 'drop in the ocean'!

Well picked up Anonymous, I would say that if you assume average output of about 30% of peak rating (a little less than a third) for UK wind you wont be too far out, i.e. a 3MW turbine will produce a bit less than 1MW average power. This may be what RenewableUK was meaning but got a bit muddled in the transcribing. However this is average.

In December 2010 there was a period where total UK wind output hardly got above 10% of peak capacity for nearly two weeks, often below 5%. This is the type of scenario when we will need some serious seasonal/longterm dispatchable storage, several TWh for the UK, if we are to integrate a large proportion of renewables into the energy mix.

On Balance though I think RenewableUK?s analysis on this is probably a bit closer to reality than KPMG?s.

mike-holly-17241,
I don't think the UK has quite the same problems as Japan and I am not anti-nuclear per se, if it was the only viable energy source I could live with it.

However having said this I don't think nuclear is desirable and am not convinced that it is necessary, an energy infrastructure based on renewables coupled with green carbonaceous fuels for energy stockpiling is, I believe, both preferable, feasible and economically viable. This may require importing some RE or renewable fuels, much as we do now, but this dos not necessarily mean reduced energy security, unless one considers energy security and independence as synonymous, which I don't. Take Iraq for example, Iraq had energy independence in spades but it didn't give them security; it's nearly 10 years on now and as far as I am aware they still haven't completely restored their energy infrastructure.

As most people who understand renewable technologies know, the biggest challenge with de(fossil)carbonisation is not technology but politics, and politics tend to be steered by economics and here lies the problem, as indicated in my previous post. Economics does not have vision, it generally crunches the numbers based on what it knows now with the aim of producing the smallest number (cost) at the bottom of the page based on data that already exists. Economics is about money, not solving problems.

I'm fairly confident that it is/will be possible to generate solar electricity for about 2p (3¢(US)) per KWh using CPV located in deserts (Sahara etc.). Even if we lost 50% in the energy storage system this is still very viable and cheaper than the options listed by KPMG. My predictions are in part based on the Aussie's CPV (SunCube) technology that can generate electricity at 6¢ to 8.5¢ (Aus)/KWh, (http://www.greenandgoldenergy.com.au/), that's less than 4p/KWh now! And there's still plenty of scope for improvement in PV technologies.

Cont'd:

Anyway, getting back to topic, UK power de(fossil)carbonisation. It is interesting to note that KPMG is basically an accounting firm (services including audit, tax and advisory), and whilst they may be very good at economics, like our energy secretary who is an economist by training. The UK power generation infrastructure is very technology dependant and I suspect that, like our energy secretary, KPMG have difficulty properly understanding the true and full impacts of these technologies. For example; I recently had the opportunity to make our energy secretary aware of a technology the Chinese are busily developing that could completely undermine our £1Bn+ CCS programme, his answer was that there was plenty of room for al these technologies. What he couldn't see was that what I was talking about was a VHS vs Beta-Max scenario, not two different companies/countries trying to sell VHS. By the way, the Chinese approach would probably be half the cost and 2 to 3 times more efficient than the one the UK hopes to sell to the Chinese!

My overall conclusion from reading this article and my personal experiences is that the people who make and comment on energy policy should be first and foremost people who understand energy technologies and be advised by economists, not the other way round as seems to be the case.

I'm not quite sure what Ocharpen is talking about in most of his/her post, or the Wiki Ocharpen article for that matter which appears to have some dubious Physics in it, but I think the underlying message is about tidal (Moon/Sun gravity) power. However I think there are some misconceptions (in the Wiki article) regarding propagation of tides. Tidal water fundamentally goes up and down, it does not go round the Earth or there would be constant tsunamis. There is a certain amount of stored energy in the world's oceans due to tidal movements which, without considering the concentrating effects of land masses, average is around 54cm (21') tidal range. Based on this figure average imparted energy, from gravitational forces, is about 1.5MWh/Km2/day so recoverable is at best about 90% of this figure.

In the UK we have a naturally occurring tidal concentrating feature, the River Severn Estuary which has a range of about 12m(40ft). With this 20 fold plus improvement in height it is still going to cost over £20Bn (~$32Bn) for a 2GW scheme. At the heights quoted in the Wiki article I would suspect that cap-ex would be at least double. They've been discussing plans for a Severn tidal power scheme since the Victorians (1800's) and the Government still can't decide whether it's worth doing.

The area of the Earth's oceans is 361 M Km2 and based on this figure TOTAL available power would be less than 20TW (assuming polar oceans have same tidal range which I doubt), and we could collect 100% of stored energy. In reality I would be surprised if we could collect even 10% of this, about 1000 Severn Estuary schemes, probably at a cost of over well over $50T.

A further point (re: Wiki article which suggests that with the Pacific/Atlantic difference of 37cm you could generate '160 GW of continuous power'), 160GW @ 0.37m and 90% conversion efficiency would require a flow rate of about 50M m3/sec, equivalent to over 25,000 Niagara Falls (@ 1,834 m3/s)!

Now this is making sense at last.

This is where bio-fuel investment and development should really be directed.

We can run cars on hydrogen or better still, and much more efficiently, on electricity, but these technologies are totally unsuitable for commercial or military aviation (except rockets), for these we have to have carbonaceous fuels and the only route to de-fossilise these is to use biofuels.

There's a limit to the amount of bio-fuels we can sensibly produce without impacting food production, so let's focus on using them for applications where they are the only practical option.

"What Free Electric the sun makes will be used to split water into Hydrogen. The Hydrogen will be used to ..." reduce captured CO2 to carbon and carbonaceous fuels that can be easily and cheaply stockpiled for use when there is no, or reduced, solar/renewable generation, e.g. stored in summer for use in winter for power generation. This amount of long-term, stable, energy storage is totally impractical using hydrogen directly but if solar energy is converted to chemical energy in the form of carbon the amount of storage and its storage life are almost limitless, Nature?s already shown us the way, it?s called coal, what we need to is to replace fossil coal with 'green coal'.

The basic approach (as hinted at in my previous post) is this:
Electric power generated directly by renewables and backed up by DCFC (Direct Carbon Fuels Cell) technology at 80% efficiency will mainly power our economy, which, with the advent of improved battery technology will include most transport, which will become affordable and at about 1000 miles range and/or quick swappable battery packs will mean that major hurdle, charging time, will not be an issue.
The 100% CO2 captured from DCFC power stations will be recycled efficiently back into carbon using 'the Free Electric the sun makes'!

However, Paul Felix Schot, when it comes to guidance I prefer to rely on my brain, my education and life experiences, because personally, based on their past record, I do not place a great deal of faith in JC or his dad to be of very much help, if it was anyone else in charge of Planet Earth plc (or inc), they would have been sacked a long time ago, so I think we're on our own with this one.

Education is a vital part of a renewable future but I it needs to go much deeper than just providing students with science and engineering skills.
The US is fortunate because with well over 500,000Km2 of deserts, in principle there is no fundamental reason why all US power needs could not be sourced internally from renewables, particularly solar. This would require massive, probably seasonal, energy storage facilities to balance the load but we do have the technologies to do this, albeit not available at commercially scale yet. The technology is CCR (Carbon Capture and Recycling) using 'Green Coal', but this is another topic so I won't go into details here.
Returning to education, climate change and sustainable energy supply is a global problem and whereas the US may be able to meet all its energy demands internally there are many countries that won't be able to, probably including the UK. In these cases energy survival will depend to some degree on cooperation and sharing of resources and to do this effectively we ideally need a stable international political environment. This is only likely to be achieved by educating all people to realise that we are all basically the same and ultimately all citizens of Planet Earth.
So, along with physics, chemistry and maths we need to educate all students, and indeed people in general, in all countries to understand the bigger picture, to think rationally and to realise that; if you still believe in an omnipotent, omniscient and omnipresent god then he/she/it created everything, not just the Jews or the Muslims or the Mormons or whatever faith one belongs to, there is only one chosen race on this planet, it's the Human Race. Therefore we should leave any smiting up to him, if he feels inclined as he should be quite capable of doing it himself, if he is real. Instead us mortals should get on with the job of saving the planet, or more correctly, the Human Race.

Previous comments ? Very true

At 2.3Mt for the remaining 8000 hours this means Tilbury uses 287.5 tonnes of timber per hour.

I found some info for timber production in Nova Scotia (www.gov.ns.ca/natr/forestry/reports/Biomass_Inventory.pdf) and at this rate Tilbury consumes about 4ha (10acres) of forest timber per hour. Tilbury's load factor is about 75% or about 6500 hrs/yr. If we assume a forest regeneration of 25y then Tilbury needs 4 x 6500 x 25 = 650000ha to support it (6,500Km2,1.65M-ac) about 12% of Nova Scotia, to generate about 1.5%, or less, of UK power demand. This doesn't include the energy required to; harvest the timber, chip it and dry it and then get the timber from North America to Tilbury either.

By comparison wind average power generation is about 6W/m2. Nova Scotia is probably quite windy so 6,500Km2 would produce about 6,500 x 1M x 6 = 39GW, about 100% of UK power requirement.

I'm not suggesting that Nova Scotia should be covered in wind turbines and there are other considerations to take into account, but it does put biomass as an energy source for power generation into perspective.

Its true storage will add capital cost but the problem with wind is it is very fickle and turbine output can vary from almost nothing to full output on a daily, possibly hourly, basis, even in Wyoming. It would not be possible to operate industry on such a flexible basis; employees would have to be swapping shifts on a daily basis. Also without storage you will need additional/over capacity to cover periods of low generation which may need to be several times the average output to give a reasonable certainty of having enough power during normal working periods.

If the wind is only supplementing the normal grid power then the problems may not be significant but in this case it still means that the grid will need to be taken to where the wind source is for backup.

Storage and interconnection are the answers, but the storage has to substantial, cheap and able to provide at least a few days of supply if wind is to be the predominant energy source. In the UK in Dec 2010 wind output for the whole of the UK dropped to about 5%, or less, for over a day on three separate occasions, two of which were for about 3 days. Wind currently only supplies a very small fraction of UK energy so conventional generation is able to make up the difference, but if wind provided a major part we would have been in a bit of a pickle.

To return to my comment regarding 'huge potential energy in deep waters of lakes and oceans' I have to admit I made a mistake.

What I should have realised is that the deep waters of lakes and oceans have water under 'huge pressure' not 'huge potential energy'. Pressure, however huge, is not in its self potential energy. Anything that's under a huge amount of mass will be under huge pressure, but this does not translate to huge potential energy unless this mass can move to a place of lower potential energy.

Arov. When you have finished testing your 'static pressure engine' what are you going to use in place of your compressed air source?

By the way, I've had a look at 'PIPS deep water static pressure to energy converter' @ www.world-wire.com/news/1010010002.html. It has two pistons that apear to move up and down under fluid pressure which is then translated into rotary motion. Moving pistons indicates moving fluid from one pressure to a lower pressure which is a perfectly normal way of harnessing the potential energy in a fluid under pressure to convert it into kinetic energy, but this does also imply a fluid flow, albeit a little different from the continuous flow through a turbine. On the basis that large turbines can harness close to 90% of the potential energy that was originally in the water stored in the dam I would doubt if there is a huge room for performance improvement.