While it is always pleasing to see the Greens pursue a widening of the PV scheme, this correspondent has yet to see any comments from the South Australian PV industry indicating similar impatience.  I strongly suspect that right now, the market is suffering a skills constraint on growth and that increasing consumer demand is not going to lead to a more orderly industry.

There is a news link which announces that this system, which was previously only recommended over timber is now available in an onto-concrete version.  This requires simply a moisture barrier such as a membrane, or a polyurethane moisture mastik.

Hydronic heating is becoming a realistic option in Australia now that efficient heat pump and rooftop solar collectors are available which work efficiently in winter.   Hydronic heating refers to using hot water to heat a space using either in-floor coils, or wall-mounted radiators.

Wall-mounted radiators are ideal for renovations or where the homeowner does not want to replace the floor.  The radiators typically operate at 60C so a heat pump system is not appropriate and the homeowner must use a solar collector.

Where a new dwelling is being built, in-floor coils are an option.   As these run at a lower temperature of 40C, a heat pump can be used to drive them.  Usually the coils are placed in the main living areas of the house, such as living rooms, dining areas, kitchens and bathrooms.  Bedrooms are often not heated, although childrens’ bedrooms may be an exception.

Wall-mounted hydronic systems have always been popular in Europe. Usually these were driven by a central steam boiler and operated at 70C+.   Because of the increasing use of solar collectors, these are now almost obsolete in new buildings, and builders now prefer pumped water circulation systems operating at a lower temperature.

In-floor heating is even more comfortable as very little convection occurs, and the perceived warmth is mostly radiant from the floor.  The advantage is that the system operates at lower temperatures, is therefore more efficient.  With evacuated tube collectors and sufficient solar storage capacity, the system can provide a greater fraction of the heating requirements.

These coils are from a durable polymer called PEX which typically comes with a 25-year warranty and a quoted lifespan of 250 years.

either a) laid into the concrete when the slab is poured, or b) laid on insulation sheets then screeded in, or c) laid on insulation sheets, then covered and the screed is laid on top, or d) laid on insulation sheets, and then covered by hard flooring.  Many different systems compete in the market place.  Arguably, if the concrete is to be covered with hard flooring, then the coils need not be laid into the concrete.  The advantages of in-concrete coils are that the concrete slab has a very large thermal mass and this will retain a lot of the heat which is required.  The other advantage is the superior load-bearing characteristics.  The disadvantage is that this system has a very long time lag, and that the coils cannot be replaced.

In Europe, which is much colder and where heating is a higher priority, there is a wide choice of options. Surveying the industry we find the following hydronic heating manufacturers and specialist installers in Germany:

Aquatherm, Emcal, Fraenkische, Gabo, Giocomini, Havekost, Hewing, IBB, Janssen, JOCO, Jupiter, KAN-Therm, Kermi, KME, Lindner, MAINCOR, MAIR, Norit, Oventrop, Purmo, RIT, Rehau, Remo, ROTEX, Roth, Schuetz, Sigmund, Solar Leidig, THERMOLUTZ, Uponor, Variotherm, Viega, Vogel-Noot, Wavin, Wieland, Zewotherm.

Perhaps what they should have done was to confine the scope of the inquiry not to systems but to components.   That way perhaps at least the industry practitioners who are constantly putting together new systems, would have a little more qualitative information with which to make the choice.   I feel that with a system where the components are customised almost with every installation, the idea is not to educate the consumer, but the industry.

The methodology of evaluating solar hot water systems should be to compare like with like.  Comparing a flat panel collector with a heat pump system is just not good enough and ends up confusing readers.

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 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

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.

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.

Evacuated Tube Solar Hot Water Heaters

Cheers.

When we talk about a Zero Net Energy home, do we actually count the embodied energy of the home?  Because if so, then the degradation of the building materials over the life of the building, must be included in the energy balance sheet.  In other words, in order to achieve Zero Net Energy, the house must generate not only the occupants’ energy requirements but ALSO produce energy equivalent to the embodied energy of the house over its life.

This is surely not easy to achieve.  But that is surely the true meaning of the term.