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Nanosolar have stated that approximately 6 square kilometers of land will be required to produce 1GW of nameplate solar capacity.  How much land is this really?  Well it is a square of 2.44km on a side.  I have superimposed such a square over the site of the Leigh Creek coal mine in the Gammon Ranges in the Australian outback.

Where is this in the scheme of things?  Let’s zoom out.

So in Summary the footprint of a solar farm is less than the footprint of a typical coal mine supplying a similar amount of coal-fired generation.  In addition, the land between the collectors can still be utilised for grazing.  The coal mining operations also require precious water, which is not required for PV.

The PV solar farm may make a lot of sense for some communities.  The concentrating PV operations like Solar Systems, might take note.

The new stars of Silicon Valley are the scientists engineers and business people of Nanosolar in Palo Alto.  Having taken their website down last week announcing that they would be back on September 9, they were true to their word.  Speculation was that perhaps a takeover was in the wind.  Thankfully this did not eventuate.  Instead the announcements were positive milestone achievements which might silence the critics of the last few years.  On Wednesday Nanosolar announced to the world the completion of their factory producing their new Nanosolar Utility Panel (TM) in a factory in Luckenwalde, and immediate availability of the panels.  This factory is a state-of-the-art robotic assembly plant incorporating the foil cells being made in Palo Alto.  The capacity of the panel plant is currently 640MW per annum.  Manufacture of the foil utilising their funky CIGS ink, is possible at a rate of 1GW per annum per machine.  The machine looks like a $2m capital item and it would not be a stretch to fit 20 of them in a small factory.   The days of the 20GW p.a. manufacturing site are now here.  Panel assembly will have to keep up.  If I was making silicon wafers for photovoltaics, I would be looking worried today.

The contractual commitments from power companies and other partners, is about $4.1bn.  It appears the $0.5bn invested by the venture and private equity partners, including the likes of Sergey Brin and Larry Page, have been well spent.  The list of investors has been pulled from their website, but the google cached version shows these investors:

• Mitsui – the 300 year-old Japanese keiretsu.
• Carlyle Group – largest investment group in the world
• Swiss Re – the largest reinsurer in the world
• Benchmark Capital – the eBay financiers
• Lone Pine Capital
• Mohr Davidow Ventures
• EDF – the world’s largest energy utility
• Energy Capital Partners
• Klaus Tschira’s First Ventury
• Jeff Skoll
• Pierre Omidyar
• SAC Capital
• GLG Partners
• LGT Capital Group
• Grazia Equity

The Nanosolar website is blacked out with a simple message saying please check back September 9.  They are obviously gearing up for a major announcements.  Speculation on other websites centers around a big announcement confirming massive commercial production ability and the general ebay availability of these printable nano-dye solar cells which have previously only been available to their German partners, and have been promising the under $1 per watt price point holy grail.

Myself I disagree – I sense a takeover by a global behemoth.  Dupont?  3M?  Dow Chemical?  General Electric?  Westinghouse?  Exxon?  I shudder to think.  Perhaps it’s positive but I tell you what – I hope it’s not a silicon wafer manufacturer.  I would hope and expect the government to step in.  Why?  Because there is a chance of skullduggery if this is the case.

Certainly there is cause for concern.   Silicon cell manufacturers are now a powerful market force.  They stand to lose their livelihood overnight if the economics of nanosolar are realised.   There are potentially thousands of jobs which are threatened.  The intellectual property has a huge strategic importance and it really should not be controlled by forces which are sympathetic to the status quo.  That is to say, forces which have a large sunk investment in the existing silicon-based technology.

This forum like many others has had lively discussions of the merits of the new evacuated tube collectors versus the old flat panel collectors and this dialog is still ongoing.  The author’s favouritism for Evacuated Tube collectors is well known.

Recently I ran some simulations with my licenced copy of the T*SOL simulation software.  This excellent package is available at valentin.de and yes if you are a plumber I recommend you get it.  I have found some interesting results.

My scenario is a laundromat where northern sun access is available.  The laundry’s demand is 2000 litres per day of 50°C water.  The usage peaks in the morning and again in the afternoon like so:

Now the monthly demand is assumed to be constant over the year.  We have a flat roof of only about 5m x 6m.

Evacuated Tube

Now using T*SOL to optimise this with a 500l stratified storage tank (e.g. Rotex or Latento), and inline gas boosting of 17kW, we should use four 30-tube evacuated tube panels (e.g. from Jiangsu Sunrain) giving us a gross surface area of approx 20 sq.m.  The solar contribution graph is then as follows:

The Solar contribution is a little over half of the energy demand.  Now how do flat panel collectors stack up?

Flat Panel Collectors

How to make the comparison meaningful?  The four ET collectors have cost us approx. $8000 or $500 per sq.m.   For that you could get say 10 flat panel collectors from Solahart and again the gross surface area is around 20sq.m.

So as you can see solar contribution for Evacuated Tube only 92% of what the FP collectors give us.  But given that this is a dollar-for-dollar comparison, it is wrong to say that the ET panels cost significantly more.  In fact they cost only 9% more (1/0.92 = 1.09).

So given that ET collectors cost a whopping 9% more than flat panel collectors, why are they taking over the world?

So why ET?

Secondly, longevity.  ET collectors just don’t degrade over time the same way FP collectors do.  Many FP collectors just out of warranty will suffer some moisture ingress into the absorber cavity, which will cause the characteristic white tin oxide corrosion you see.  The system still works, but the efficiency is degraded.  How much I’m not sure but I bet it’s more than 9%.  In comparison the ET collectors degrade less, and they degrade differently.  Typically one of the tubes will lose its vacuum for some reason (perhaps someone threw a brick at it!)…This is a $30 end-user replacement and no plumber is required.  In the meantime the system still performs almost as before, with 96% of the original efficiency.  Throw a brick at a FP panel, and you will need a new panel – and a plumber!

Frost-tolerance is far better.  The ET panels from Hills Solar are rated to -15°C here in Australia covering ALL country and alpine areas.  A flat panel collector would require a glycol solar loop in such areas.  This requires  a heat exchanger in the tank and an expansion vessel.  Not to mention ethylene glycol, which is not so eco-friendly.

Installation is easier.  The installer can carry the 15kg manifold piece up the ladder and attach it to the frame.  Then the tubes can be carried up and installed separately.   For a FP collector, two installers or a crane are required.

Lastly, the cost differential between ET and FP is declining.  Anecdotally I have been told that there are approx 1200 manufacturers of evacuated tube collectors in China.  Personally, I find this hard to believe.  I can believe there would be 1200 brands globally, all made by perhaps 20 manufacturers, most of them willing to brand their products.  The point is still valid, that evacuated tube collectors for hot water are the future, and the flat panel type are a thing of the past.

Hi i thought i should repost a link to a popular topic from a while ago.  There are 133 reader comments to date, and many of them quite informative.  Here’s the original post

Evacuated Tube Solar Hot Water Heaters

Cheers.

If you are thinking of inventing or launching a new product then take heart.  Don’t be discouraged or disheartened.  Nothing is that difficult.  As part of your research you might have investigated the competition, and found an daunting degree of product sophistication.   It seems that everywhere you look, the techniques are difficult, the results are entirely dependent on a staggering amount of specialised expertise, and the barriers to entry are insurmountable.  I will let you in on a secret:  Manufacturers everywhere try their best to make what they do seem difficult.  Manufacturers do and say whatever they can to discourage you from competing with them.  One of the key ways to do this is to pretend that what they are doing is infernally difficult.  Perhaps elements of what they are attempting are difficult, but often these are product embellishments which add very little to the product performance.  Often the real difficulty with any of these products is getting them to market successfully.  The technology often is not that hard.

So many things in this world are now available off-the-shelf or can be made-to-order.   Just look at Alibaba for inspiration.  The clever inventor usually just needs to find a way to view these products as modules which can be endlessly recombined to achieve new products.

The world is once again beginning to take an interest in refrigeration devices without moving parts.  More precisely, Oxford University has taken an interest.

This fridge is interesting purely because of the rather famous name on the patent:  Albert Einstein.  However it seems that the real inventor was his colleague Leo Szilard.  Albert, who was already famous in 1927, consented to put his name on the patent in order to lend it prominence.

The patent was purchased by a competitor.  The details are on wikipedia.  The low-tech but low-yield technology was sunk under the weight of the vastly more efficient mechanical vapour compression technology we have come to love, and that is where it has sat for the last 80 years.

Now there are some reasons why there has been a resurgence of interest.  With evacuated tube technology, CLFR concentrators, and rising fossil energy costs, the time to revisit this area has never been better.

Presumably the patent has also expired.  Mostly it is just interesting for its own sake.  Researchers at Oxford University have claimed that with a different choice of gases, the efficiency might be greatly improved.

What follows is my own layman explanation of how this fridge works, and some thoughts on the challenges of building one.

Basically the picture from the patent application is as follows:

Now as for the parts which have been labelled:

1 – Evaporator containing liquid butane.  This is the cold part

5 – Conduit linking evaporator and condenser.

6 – Condenser where butane gas is recondensed.

12 – cooling water jacket

26 – ammonia solution

27 – conduit

28 – heat exchanger jacket

29 – generator, heated in any suitable manner.  Contains ammonia solution.

30 – conduit

31 – distributor head introducing ammonia gas

32 – conduit

33 – container of hot weak ammonia solution

35 – distributor head spraying water.

36 – source of heat

37 – conduit

Now container 1 will be applied to the body to be cooled.  The heat source will be applied to container 29 and the conduit pipe 36.

The cooling is effected by ammonia gas being introduced into container 1.  This causes the liquid butane to boil and produce the cooling effect.

The butane gas travels to condenser 6 where water is introduced in order to dissolve and thus remove the ammonia.  This causes a liquifaction of the butane which is then available for reuse.

The strong water-ammonia solution at the bottom of the condenser 6, flows through a cooling jacket where it is used to cool the hot weak ammonia solution coming from 33.

More heat is applied to this strong ammonia solution in 29, to drive off the ammonia through 30, where it is cooled in cooling jacket 5, before being re-introduced into the evaporator to continue the cooling effect.

So that’s it.  On the Alibaba site, you can find any number of adsorption chillers.  These all use 80C water, say from a solar collector, to dehydrate a lithium bromide brine which is an exothermic reaction.  The brine can then be cooled to ambient and when it is rehydrated, it chills water by about 10C.

The Einstein Szilard fridge could become another alternative to this.  After all we know that lithium has other more important uses.

For a comprehensive thermodynamic analysis, read this paper published on the Georgia Tech website.

OK I have really done my homework here and reached some strong conclusions.  The key component in a solar hot water system is not the collector – it is the tank.

There are around 1200 manufacturers of evacuated tube collectors in China alone.  They vary very little in design and their efficiency does not vary much either.  Due to manufacturing differences and quality differences, they might differ in their longevity, price, service and support.  Pumps, pipes, controllers – well they vary but mostly the systems for sale here in Australia use adequate quality parts here.

All solar hot water systems require a storage tank.  Now the performance characteristics of the tanks are extremely important.  The amount of thermal loss, the convective losses, the conductive losses, the lining material, the placement and shape of the heat exchangers, diffusion baffles,  boosting elements – all these things make for a wide variety of performance characteristics for what might be the same size tank.

What you are trying to achieve is the most efficient uptake of thermal energy, and the greatest energy storage capacity, and the greatest lifetime.  Also important is ensuring that the water can be delivered without legionella risk.

To ensure the most efficient uptake, all storage tanks rely on stratification – that is – the hot water stays at the top.  This ensures that the collectors are heating cool water, not hot water.  The efficiency of the energy uptake is proportional to the temperature difference.

To do this, it turns out that direct-flow tanks are not ideal, because it creates too much mixing.  It turns out the heat from the collectors is best delivered with an in-tank heat exchanger near the bottom of the tank, and an inverted funnel above it which allows the hot water to convect to the top with a minimum of mixing.  The water heat storage medium is thus not at mains pressure, but at atmospheric pressure.

Another innovation which recently hit the market is the plastic tank.  Almost all tanks sold these days are still made of steel, either marine grade, or enamel coated.  Using a thermally conductive tank liner is no longer worlds-best-practice.  Too much heat conducts from the top of the tank to the colder layers below, destroying stratification.  The best tank material for solar storage tanks is actually thermally insulating plastic, and polypropylene in particular.  So far the only such tank is the Latento which has a polypropylene inner skin (melting point 160°C), a thick polyurethane inner and another UV-stabilised polypropylene outer skin.   The design life is apparently 47 years.  A steel tank could not possibly compete.  When you think about it, the working temperature of the tank will never exceed 95°C, so there is a huge margin.  Also, the water in the tank is not the water you drink (if you ever drink hot water from the tap that is).

This of course means that the usable heat must be removed from the tank by another heat exchanger.  No problem either.  In fact there is a huge benefit, because this water has been freshly heated to its useful temperature.  There is no time for legionella to take hold.

Incidentally the heat exchangers used in the Latento are corrugated stainless steel with coarse corrugation.  INot sure why you wouldn’t use copper except that price must be a concern, and consumers believe they get better water quality if the water flows through stainless pipes.

That’s it – the Latento is the best tank there is.  The water is at atmospheric pressure.  It uses up to 4 heat exchangers.  It is made of polypropylene not steel.

Oh and did I mention it has a layer of paraffin wax floating on the top of the water.  Ingeniously, this allows it to store the latent heat of melting, when the wax melts at 65°C.  These 500l storage tanks can store about 50kWh – see whether any other tanks publish how much they can store in terms of kWh.

The only problem is, they are hellishly expensive.  Apparently a 500l tank is around AUD $10,000.  They are made in Germany (where else!?) by highly-paid German engineers, and not made anywhere else.  Apparently they are currently used in commercial and industrial settings where this extra money is not an issue, given the extra performance over the life of the system.

For domestic hot water – wouldn’t it be nice if a somewhat cheaper clone existed?  Something made by a rainwater tank manufacturer and available down at your Bunnings for a thousand dollars?  That’s all it needs to cost if you ask me.

Don’t you think that the media gets a little too close to the action sometimes?  When reporting the daily excitement (such as it is) of federal politics the columnists often ignore the details of the legislation.  And they still opine on the meaning of it all, but are often too taken with the personal politics and not the policy and the legislation.

It is true that too many readers (or viewers) lack the patience to wade through the details of the legislation being debated, and they just want a simplified picture.  I am not one of those.  I just care about the legislation in its own right.

I set out to find the answer straight from the horse’s mouth.  Without the media spin and the parliamentary BS.  Here’s how I went about it.

I googled “federal hansard” and eventually found my way to the Federal Government Hansard pages.  These pages are not very useful in themselves because they are not searchable.  They did however point me to the Parlinfo site which is the central portal for searching all parliamentary document collections.  I went to the Parlinfo Advanced Search Page here and then enter the search term of CPRS.  Then I ticked to search the Bills Digests.  My search resulted in 14 documents.  I chose the Carbon Pollution Reduction Scheme Bill 2009 and got a PDF file, of 94 pages and well-written.  It is a lucid explanation of what is being attempted, with the politics and the legalese removed.  A layman like myself can make sense of it.  The Digest does warn that it has no legal status and other documents should be consulted about subsequent amendments.

Jump to Page 15 for an Outline of the scheme, which essentially explains that the CPRS is a cap-and-trade scheme whereby the government sets an annual limit for GHG emissions, the government then either sells or issues emission units to liable parties such as power generators, who must then either buy or sell additional emission units in line with their actual CO2 emissions.  The liable parties are then required to surrender the emission units equal to its emissions over the relevant financial year.  If they do not then they are subject to a penalty.  The Australian model CPRS departs from the classical cap and trade model in that it sets a fixed price on an emissions permit for the first year and an upper limit on the price for the following four years.

Oh I have to tell you these guys were not easy to find!  Incredible how little good information trickles out to the informed enthusiast, let alone the average consumer.  So following on from yesterday’s post on the merits of polypropylene solar storage tanks, I thought I would find whether the leading brand Latento, had any competition.  It turns out that they do, and they are in Australia.  NSW to be exact.

The brand is ROTEX Australia.  It beats me why more people have not heard of it.  Like Latento their Rotex Sanicube tanks are made from polypropylene, with the same benefits.  They also use heat exchangers, but with one major difference.  The Latento solar loop is closed loop, whereas the ROTEX one is direct flow (also known as drainback).  So the stratification could be less efficient.  It’s hard to tell.  That said, it would not be hard to adapt the tank and fit a solar loop heat-exchanger in the bottom of the tank.

And another thing – what would stop a consumer from draining 20 litres from the tank and replacing it with paraffin wax for better performance, and less evaporation?  Nothing.

Update from the field.  A little more research reveals the Rotex tanks are also made in Germany.  They are around AUD $5000 each!!!