Photovoltaic [pv] panels to generate electricity have been in the UK news recently;- http://www.currys.co.uk/solarpower/index.html
[Currys is a large UK electrical retailer.]

The system they are selling is by 'Sharp'.
Summarised, from their website;

Roof mounted panels: Currys quote a value of 1600kWh/annum produced from a 'typical' system having a rating of '2kWp' (whatever that means. They say it means 1kWp = 800kWh/year! 2x1 = 2 ). The pv units carry a 25 year warranty. The panel[s] supply dc output to-

An externally placed inverter. This creates ac of poco 'quality' and sync, which feeds to-

A 'production' meter, feeding power direct to the National Grid. Customers will be paid/credited for this power. [ Not all of the present UK pocos, some of whom are actually just 'brokers', will do this; a customer may need to change to a company that will. ]

The poco supplies electricity to the customer from the Grid via a second 'consumption' meter.

Note; There are no batteries, the customer is still Grid connected, and all the power actually consumed in the home comes from the Grid.

Technically, this is quite a neat scheme. It retains the security of being Grid connected and it retains the home's existing panels/fuses/breakers and other safety features etc.. There is no battery system, which reduces complexity, maintenance, storage and first cost. As long as the Grid is up, you have power. You have power at night, and your pv generation to the Grid is paid for. At what price per kwh is not revealed, of course.

Furthermore, Linesmen safety is assured because the system shuts off automatically in the event of a power outage; it won't backfeed the local transmission lines.

Quote: " There is no product that can be added to [the] pv system to act as a back up at the present time".

The present cost is 'from' £9000 for a 'complete package' generating about 1600kWh per annum, and consisting of 9 arrays and all the necessary kit, fitting, wiring etc..
Currys are naturally reticent about payback, and waffle a bit about 'increased house-values', a much cherished UK phenomenon; but I reckon straight payback, based on power generated, at about 66 years at present UK power prices.

Solar power arriving on Earth as light, [ ie photons, the 'fuel' of these devices], is quoted at about 1 kw/ square metre, [1 kw/ 10 sq. foot] in mid-lattitudes. Efficiency of conversion is about 10-15%. One US website quotes an output of c 10.75W/sq. foot, or 1kw per 93 sq foot ( ie. a square of 9ft 6" sides ) of panels. This would vary during the day /time of year/ lattitude, of course. Prices per square ft. vary enormously, as you would expect, but a price of US$6000 per kw output [US$65 a square foot] has been seen quoted on the net.

All I can say is, they are not going to get killed in the rush on those figures. The cost has to come down, perhaps through grant aid / tax breaks?

Alan

I did some calculations a while back. The problem isn't the cost of the panels, it's that the sun really doesn't put all that much energy onto the earth- we would have to pave an incredibly large number of square miles of earth to satisfy the energy needs of a major western nation.

FYI, it would literally take a solar panel larger than Wales to supply UK with your annual electrical consuption. And probably require most of Scotland to be turned into hydoelectric resevoirs to feed the grid at night and on rainy/cloudy days.


Assumptions/Constants:
* Average Solar Flux for North America: 150 W/m2 -This is representative of the US Northeast and Europe, and accounts for weather.
* Best Average Solar Flux in the US southwest is 240 W/m2
* Northern US December average 71 W/m2
* Winter levels will be appx 80% of this value
* US Annual Energy Consumption in 2003: 6.22 ExaWatt-hours (equivilent to 325 billion tons of oil)
* Typical electrically heated household energy use during coldest week of winter: 24,000W
* Typical instantaneous power requirement for a refrigerator: 1200W
* Combined contribution of solar, geothermal and wind in 2003: less than 2%
* Solar Panel Efficiency: 8.25% (commercially mass produced a-Si, the only feasible material at the scale we're talking! See Unisolar whitepaper #1 below.)
* Thermal de-rating of solar panels for US winter weather: 15% for a-Si, 35% for crystalline silicon.
* Typical loss due to dirt, dust, etc: 3%+
* Inverter efficiency: 94%
* Wiring efficiency: 97%
* Transformer efficiency: 95%
* Battery efficiency: 80%

* Energy required to manufacture a-Si panels:120 kWh/m2 (432 MJ/m2) as a generously conservative estimate. I don't know if this counts mining, refining, transportation, installation, cabling, power conversion, substations, transmission, etc, etc and I'm pretty sure it doesn't.
* Energy required to mount an a-Si panel: appx 120 kWh/m2 (432 MJ/m2)

* Solar energy absorbed annually per m2 in US Southwest desert:
365 days * 24 hours * 240W/m2 = 2,100 kWh

* Solar energy absorbed annually per m2 in US Northeast:
365 days * 24 hours * 150W/m2 = 1,314 kWh

* Losses in conversion, wiring, etc:
.97 * .94 * .97 * .95 * .80 = 32% loss, 67% efficiency

* Break-even point for energy for a-Si Solar Panels and installation in US Southwest desert:
240kWh/m2 / (240W/m2 * 8.25% * 67% * 24 * 365) = 2.1 years

* Break-even point for energy for a-Si Solar Panels and installation in US Northeast:
240kWh /m2 / (150W/m2 * 8.25% * 67% * 24 * 365) = 3.2 years

For this that missed the significance of this, it means spending 2-3x our entire annual energy consumption on solar panel production alone.

If the south-facing roof of a 200m2 (~2000ft2) typical house in the Arizona desert was covered in a-Si solar panels:
240W/m2 * 100 m2 * 8.25% * 67% = 1300W (about enough to run a refrigerator)

If the south-facing roof of a 200m2 (~2000ft2) typical house in the US was covered in a-Si solar panels:
150W/m2 * 100 m2 * 8.25% * 67% = 829W (about enough to run a typical PC desktop with 17" CRT monitor). It would take 42 houses like this to provide the energy one house requires for electric heating.

If the south-facing roof of a 200m2 (~2000ft2) typical house in the US Northeast in winter was covered in a-Si solar panels (assuming no snow):
71W/m2 * 100 m2 * 8.25% * 67% * .85 = 321W (4 houses combined could run a Mr. Coffee). It would take 75 houses like this to provide the energy one house requires for electric heating.

Cost of 8% efficient a-Si solar panel: appx $1000/m2
Cost of installation: appx $100/m2
Cost of 10kW inverter: $12000 (For surge. An electric range draws 10kW.)
Cost of storage batteries: $200/kWh
Cost of cabling: appx 1x material cost
Cost of electrical installation: appx 2x electrical material cost

100m2 of solar panels: $100,000
Cost of panel installion: $10,000
Batteries required to store 2 day’s worth of energy at 1300W average: $13,000
Cost of inverter: $12000
Cost of electrical installation: $50,000
Total cost of 1300W Arizona or 564W northeast partially-solar-powered house calculated for above: $185,000.

Area of solar panels in the southwest US desert required to supply US with total electricity demands:
6.22Ewh / (1300W * 24 * 365) = 54,000 km2

Number house-sized solar panels spread evenly throughout the US required to supply US with total electricity demands:
6.22Ewh / (829W * 24 * 365) = 856 million house-sized panels (compared to 120 million households in the US, which includes aparments and townhouses)- works out to about a quarter acre of solar panels per every family in the US. BUT, that's lopsided as most of that comes from the summer. If we go by straight winter values, it works out to closer to 17 acres of solar panels per family.

US GDP: $ 11.75 trillion
856 million house-sized panels: $158 trillion


Sources: http://www.eia.doe.gov/emeu/cabs/usa.html http://www.johnstonsarchive.net/environment/solartechnote.html http://www.uni-solar.com/uploadedFiles/0.4.2_white_paper_2.pdf http://www.uni-solar.com/uploadedFiles/0.4.2_white_paper_1.pdf http://www.nrel.gov/docs/fy04osti/35489.pdf http://en.wikipedia.org/wiki/Solar_power


Since we're using very large numbers here:
1,000 Thousand Kilo k
1,000,000 Million Mega M
1,000,000,000 Billion Giga G
1,000,000,000,000 Trillion Tera T
1,000,000,000,000,000 Quadrillion Peta P
1,000,000,000,000,000,000 Quinillion Exa E

[This message has been edited by SteveFehr (edited 08-12-2006).]

Excellent response Steve.
It is going to take me a while to wade through all that info, but a few points-

1. The Sharp/Currys system does not claim to produce all the electrical power in a UK home. At an average 3300kWh/annum UK electricity consumption, a 1600kWh/annum system would produce roughly 50% of it.

2. Based on an average European solar radiation at surface of [say] 1000kWh per sq.m, and 8.5% conversion x 67% efficiency, then to produce 1600kWh/year requires c.28 sq m of panels = 9 panels of c. 3 sq.m.
So, the system is technically viable for what it aims to achieve, it is just too expensive.

3. Most UK homes use fossil fuel for heating, with very poor insulation in most of them. I quite agree that to expect pv cells to generate enough electricity to run all the home-energy requirements of our existing housing stock is impossible.

4. Cover Wales in pv cells?
What a tempting notion!

Alan

Yeah, most solar houses cheat by using gas heating and cooking. I say BAH! If we're trying to go all solar and energy independant, you don't use fossil fuels for heat. So, with that in mind, I don't like to use the "average" household power requirements. Of course, I'm still using the overall US electrical consumption- if we went all electrical for heating and cooking, we'd likely need far more panels than I've estimated for...

Last forum I posted this on had no problems with most of my calcs, yet horribly balked and decried my $50k estimate for electrical installation costs at industry standards, including O&P and subcontracting fees. I was figuring watertight conduit and cabling run on a roof under solar panels as being extremely expensive, not to mention the cost of installing the inverter and battery bank. But I never actually sat down with Means to do a proper cost estimate, and if panels were designed for series connection or with integral power channels, that would drop the cost considerably as well. Perhaps someone else here would care to take a stab at a more accurate estimate of installation cost? Anyone here done any solar installs that might be able to help with a basis of comparison?

[This message has been edited by SteveFehr (edited 08-13-2006).]

Some research reveals that grant-aid, towards the cost of purchase of 'reducing carbon emissions equipment' , [such as pv panels ], is available in the UK and France as part of Kyoto accord. So it's probably available across the EU.

UK. Grants are available for pv panels, wind generators, hydro, etc. with provisos like mandatory additional improvements in insulation, fitting double glazing, auto furnace-controls, etc..
For pv, the grant is £3000 per kWp, up to a max. of £15000, but not more than 50% of the installed cost.
http://www.lowcarbonbuildings.org.uk

Not available in the IOM or the Channel Islands, and not available retrospective of existing purchases.

France. A very much simpler sheme, [ for a country so in love with dossiers and bureaucracy!]. Simply purchase/have fitted any energy/CO2 saving device - loft insulation, double glazing, condensing boiler, geothermal heating, pv panels, solar heating, wind turbine, closed wood-burning stove, etc., and get between 15% and 40% of the cost (less labor) knocked-off next year's income tax, on production of a receipt; pv attracts the 40% remise. Receipts are simply stapled to your annual tax form. Mine went in last month!
If you pay little or no tax, they send you a cheque instead!
The wood-burner counts, because the CO2 comes from a resource renouvelable

I'm off down the Hotel des Impots [tax office] tomorrow to see if I can get a cheque for the 200 sq metres of rockwool I just put in the remodel!

Alan

We can tax-deduct certain energy saving materials in the US, too.

Alan,
Good thread mate!.
I've said here before about a mate of mine that has a solar system that he derives power from to run 90% of his power needs.
He still has the mains running to his house and he uses it for the occasional running of his range and the washing machine.
Where his is different, however, is that his is totally independant of the mains supply, the systems are seperate.
He has (I think) 9 panels, feeding into an array of 2V cells (Ex-Telecom cells) wired in banks to give a 12V output to a 2000W Sine Wave Inverter.
He has a heap of current monitors and all sorts of other gear associated with it, it's pretty involved.
He did have an ordinary old Square wave inverter when he first started the system, but the local Radio Inspector pinged him for excess RFI, it was found that the Inverter was radiating a signal that could be measured quite a way down the street!.
Bear in mind though, that this guy doesn't use a lot of power, he lives by himself and has a fire to heat his water and his house is so well insulated, it's a wonder the bricks haven't started popping out of the outside walls.
His favourite question at Radio club meetings is:
How much was your power bill last month?.
He only pays a few dollars above the line charges, it makes me sick.

Just been looking at an interesting alternative idea.

Iceland has an unused potential hydro electric capacity of vast size, [ 26-31 TWh / year ] which the government there wants to export to Europe.
They also have 14TWh / year of unused geothermal.

The idea is this; instead of running a bit of bell wire to Sweden and all points south, make aluminum from bauxite instead using hydro-geo power. This would be shipped in 20,000 ton cargos to Europe/N. America where the electrical energy in the aluminum would be reconverted. All 280GWh of it.
BTW 'Google Earth' is a good way to get an idea of the distances involved.

Aluminum represents 6.4 kWh of electricity per pound of the metal. It's a safe non toxic cargo.

Once the electricity has been created and fed into the Grid, the aluminium hydroxide waste-product, ( ie bauxite sludge ), formed in the reaction is shipped back to Iceland and made into ....er...aluminum! The sludge is high value, because it is pure. The preparation of raw bauxite for the smelters involves costly removal of impurities like iron and silica.



Hey! Can we run cars on aluminum wire?

"Fill 'er up! 200 lbs of #6!"

Alan

delete duff link

[This message has been edited by Alan Belson (edited 08-21-2006).]

[This message has been edited by Alan Belson (edited 08-21-2006).]

Hydrogen might be a better idea, although a little more unstable than aluminumm, it is easier to haul, and easier to convert back to electicity, with no bauxite sludge to return.

Many types of poweful aluminum batteries have been built in the last 50 years, and it's true that formation of bauxite sludge/gel is a major bottleneck to releasing the potential of this metal's capacity to store energy.
I read a follow up report that a new battery is being claimed, by Europositron in Finland. This is an Aluminum battery with a claimed density of 1330Wh/kg, 3000+ cycles, life 10-30 years and -40F to + 159F working temperature and which claims to sidestep the hydroxide sludge barrier.

This is BTW only about twice the capacity of Glen Amatucci's Telcordia Technologies [Morristown NJ] 2002 patent No 6,482,548 claim for an Al-Li cell, so not outside the realms of reality.

If giant batteries can be made economically to transport electricity by ship from hydro plants, there is no sludge to carry back, just enough charge for the electric propulsion units to return the ship to the hydro power station's distributors.
http://www.europositron.com

Alan

[This message has been edited by Alan Belson (edited 08-22-2006).]

Can you approach the energy density by charging up capacitors at a useful voltage?

How about high mass flywheels motor generator sets?

LarryC

It all comes down to $, in the end. All the battery/kinetic, etc. solutions have the problem of weight. For a vehicle; ship, plane or car, weight = money.
The Europositron battery, if it can be made commercially, still stores only 10% of the energy per pound of gasoline*.

Flywheel problem ditto. No known material is able to withstand the huge hoop stresses needed, [ say 2 million psi ] to achieve comparable storage capacity kWh/lb. And a flywheel containing the energy of 10 gallons of gas in a crash would probably take out 2 blocks if it burst!

* The person who really unlocks a practical way of using Aluminum/hydrogen/WHY for vehicles will be made:
Europositron, 2065 btu/lb = 0.6kWh/lb
Gas, 23000 btu/lb = 6.7kWh/lb
Al.[to Al(OH)3] 22000 btu/lb = 6.4kWh/lb
H2 [to H2O] 60000 btu/lb = 17.5kWh/lb

We ain't there yet!

Alan

LarryC, after my hasty last post, I did a few calcs on 'flywheel' energy storage, with some interesting and positively 'hat-eating' results.

Let's look at a plain steel-disc flywheel.
For ease of calculation, let diameter be 24" and thickness 1".
Weight 131 lb. Mean diameter, [c. of gyration, all forces assumed to act at ], = 17".
Let rpm = 24000.

Mean V; 24000/60[secs] x 2pi x 17"/12 = 3560ft/sec.

Kinetic energy; 131x3560x3560/64.4[2g] = 25780149ft.lb. giving 582.6 kWh

In a plain disc flywheel, stress is at maximum at the center, reducing toward the rim. But a flywheel can be contoured progressively, [thinning rimward], to show equal hoop and radial stresses at every point while rotating. This contouring also increases the energy stored per pound of weight. The above flywheel, same approx weight and centre of gyration diameter, but contoured, would have hoop and radial stress of about 50 tons/sq. inch throughout.
Alloy steels can be made to achieve the above as working stresses, but not in large 'ruling sections'*, [ and here I am thinking of big ship-mounted flywheels transporting hydro-power].
[* This is for practical heat-treatment reasons ].
Large wheels could, however, be laminated from thin plates and / or by the use of composite materials such as carbon fibre. There are technical manufacturing difficulties here, not least the need for perfect balance and getting big wheels to run and stay true for a long useful life.

OK, let's build a machine round our shiny new 24" contoured flywheel. If the shaft, casing etc. weigh 70 lb. = 201 lb total, [ and I'm assuming here we go gaga with someone else's money and build a 'vaccuum casing' and special low-friction bearings to reduce our drag losses]. Our machine performs 582/201 = 2.9kWh/lb.
Only 43% that of gasoline but more than 3 times Europositron's claims. And this is today's technology for the investors to risk their capital on, no 'ifs' or 'buts'. Our machine, properly built and maintained, could do much better than 3000 cycles, and with no pollution. However, note that our losses will be time dependant- eventually friction will dissipate all the stored energy, so rapid transport and use is necessary for a viable scheme.

Now, although 'shaft' or 'electrical power' is often expressed or compared with 'heat units', they are not the same! Heat energy in a gas is chaotic, the motion of the molecules is in all directions. The primary purpose of a heat-engine, [ turbine, piston engine, etc.], is to [ what I like to call ] "tidy up the energy and arrange it in straight lines". In doing so a heat-engine incurs unavoidable thermodynamic losses- [ Google; Carnot's Cycle ]. 75% loss in a gasoline engine, 60% in a diesel. But flywheel energy is already 'straightened', [ as is electrical energy, BTW ]. Gasoline may have 2.3 times the kWh of our flywheel per pound, but put it through a piston engine to get shaft power and it only gives 60% as much!

So, the Big Ship sails on the Allyally-oo on the 1st day of September, and on board are a bunch of flywheels humming expectantly with stored energy. On arrival in NY or Liverpool, we couple and run generators to extract the power and run it to the Grid.
One design possibility might be to have a motor-generator permanently in-line with each flywheel, simplifying layout and charge/discharge to the operation of a simple clutch once speeds are synchronised. Electrical output will vary with the gradual loss of speed on discharge of course, but this is not a problem with solid-state devices creating the sinusoidal power output to the grid.

Larry, this shows some promise!

Now, where's my Fedora sandwich?

Alan

So all we need is lossless conversion into and out of the flywheels, lossless storage, and suitable transmission facilities at both ends. Patent office here I come!!!

Magnetic bearings for the rotating assemblies. Vacuum housings to remove windage losses. Superconductor motor generators. Plus the ship doesn't rock and roll so much.

LarryC

Brought this thread back out of the mothballs.

It occurred to me that a larger stationary version of this would be the bee's knees to assist wind power generation with shifting winds and semi-abrupt changes in wind speeds. No need to be portable, could be placed on the DC bus of the inverter to provide a means of limiting the power surges into the inverter, scalable, etc.

Placed at substations and point of use, these could be "charged up" at night to help with base loading.

My question is how would you couple power into and out of the flywheel? Obviously you do not want to use brushes and sliprings or communtators. Can magnets handle the forces needed? How fast can the system speed up and slow down in response to abrupt step changes in power flow?

This a great thread guys, we need more of these here!.
One other thing that is being sold here, quite prolifically so I'm told, is the solar water heater, it is a unit that is totally self-contained and is installed on your roof.
It works on UV light not actually heat from the sun, so even on a cloudly sort of day, you can expect to get a reasonable supply of hot water.
Now considering that Hot water is a large degree of people's electricity bills, would it make sense that solar panels and this thing would make a house a LOT more energy efficient?.

As far as flywheels are concerned for storage of energy in a fixed location, the precision balancing, bearings and construction costs might favor simpler technologies.

Consider a very simple machine, attached to a wind turbine/group of turbines/farm. Simplistically a rope hauls up a weight so arranged to turn an alternator shaft when it is allowed to fall. Such a low-tech device would literally last forever and cost less to build and maintain than a complex flywheel arrangement.
Let us again go mad with someone else's money. Bore a vertical shaft alongside/under the mill, say 40 feet in diameter and 600 feet deep. Let’s say a 2000 ton concrete ‘piston’ 40 feet long were lifted up the shaft 500 feet during times of excess production over demand. The potential is 2240 million ft lb. of energy or c. 850 kW hours.

Consider the production of hydrogen, by electrolysis, at a wind-farm site.
On May 2 1800, Mr W Nicholson and Mr A Carlisle happened to put a drop of water in contact with two wires from an electric battery. They noticed small bubbles of gas forming at the tips of the wires, which were not in contact. They then put the wires into a glass of water and found that gas was evolved from both wires. The gasses were oxygen at the anode and hydrogen at the cathode. The gasses were then mixed and exploded, when the product was found to be water. Two volumes of hydrogen were formed to each volume of oxygen. By Avogados theorum, [1811], the explosion of 3 volumes of ‘electrolytic gas’ produces 2 volumes of steam.
BTW, anyone thinking of copying the above experiment should be aware of the dangers of ‘electrolytic’ or ‘detonating gas’ - it is powerfully explosive.

The hydrogen could be used directly by fuel cells to produce electricity at times of lower wind speeds or peak demands. The electrolysis itself is theoretically 80-94% efficient with modern developments, so overall efficiencies producing electrical power would be lower, perhaps 40-60%. Oxygen production, as a by-product, might be viable to add to the overall earnings from the plant.

Alan

Indeed, hot water is the second greatest energy consumer in the home, after space heating and cooling (food refrigeration is third). Solar hot water is much less expensive than photovoltaics, and is the most cost-effective application of renewable energy there is (other than clotheslines).

If you live in a climate with no hard freezes, the technology is simple and relatively inexpensive. If freezes are frequent or of long duration, system design must include glycol loops, circulator pumps, and heat exchangers, which adds to the complexity and drives up the cost, but even cold climate systems have a favorable payback time compared with electricity.

The most cost effective application of solar hot water is for swimming pools, because the delta T involved is very small and the amount of water to be heated is huge. A typical pool system consists of cheap black plastic tubes and a single circulator pump.

My thought of the stationary flywheel storage system is more for smoothing of the changing output of a large wind generation facility. Since most generators have to be spinning in order to supply power during any lulls, the more unstable any one generation source is, the more "cushion" one needs to absorb any transients.

I believe that Germany has an electric grid stability problem because a significant portion of their generation capacity is wind powered. When a weather front moves through the area, the ouput of the wind driven generation fluctuates significantly. These fluctuations can wreak havoc, especially under extreme load conditions.

Here in the 'colonies', our interconnect grid is so huge that variations in one geographical area can usually be offset by generation outside the affected area. Plus, at this time, wind is not a major generation source.

I agree that H2 generation is a load that doesn't really care about short term variations too much. Along the same lines, most pumped storage plans probably don't care either. However if wind is going to become a significant player in the grid connected generation, I believe that it would be VERY helpful to have it contribute to the stability of the grid, not unsettle it.

I have solar hot water and I live in an area with hard freezes(Maine). The system has been installed since the early 90s and has been running ever since with zero maintenance. 2 -3 by 8 panels, a soft tank, differential controller, bronze pump, heat exchanger and some piping. Its a drain back system and works great. Its pretty much useless in late november, december and january as the sun is pretty low in the sky
but come febuary I can get water as high as 160 degrees f.