SolarHome

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!!!

I hear that electric resistive floor heating coils are still selling like hotcakes.  These heating coils are laid into the concrete footing when it is poured.  Homeowners love the comfortable, draft-less warming and it is said to be the best possible form of heating – where heating is required.

Isn’t it time we outlawed these scandalously squanderous wasters of electrical energy?

The invention of evacuated tube collectors, and the availability of efficient solar storage tanks, has made resistive heating unnecessary.   Solar hydronic systems are better, and have a far lower cost of ownership.

it is an outrage to be taking the heat energy from burning coal, turning it into electricity, and then transporting it into your home, only to turn it back into heat.  When heat is so easily extracted directly from the sun.

The same goes for electric radiator heaters.  Because of their low price and portability, they are purchased especially by the poor and disadvantaged.  Those who are too poor to put in a $3000 solar system.  Those who are least able to afford the initial outlay of something more efficient.  Those who are least able also to afford the crippling electricity bills which usually entail, when electric radiator heaters are used.

Are we saying that the poor will have to fork out or freeze?  Let’s be real here – in Australia no-one freezes.  The Australian climate is so temperate it is perfect for this measure.

I realise you might say this a nanny-state solution.  You might say let the market sort it out.  Well we already have a plethora of electrical safety regulations which are state-administered, which impose a considerable cost burden on most electrical products and even outlaw many of them already.

This would just be an extension of the existing electrical product regulation.

Next week in Munich the European Solar Thermal Industry Federation is meeting for two days from 25-27 May .

Attending from Australia will be Ken Guthrie from Sustainability Victoria, presenting a session entitled: “Mainstreaming Solar down under”.  From which we can take that solar is not yet mainstream in Australia.  This sounds about right.  I will try to contact Mr Guthrie and see whether he can blog here about his findings at the conference.  It ought to be interesting.  Certainly I can understand that the European Focus on solar space heating will not be quite so relevant here, but the sessions on Solar Thermal Cooling and airconditioning should certainly be interesting.

Other talks on the programme are:

• The role of solar thermal today and tomorrow
• The European Market for Solar thermal, current state and future development
• Energy [R]evolution scenarios
• The new European and national policy framework for solar thermal
• The new legislative framework for renewable energies in Europe
• Solar Obligations (by which they mean government incentives and directives…)
• Awareness raising and marketing
• European Solar Days – a successful awareness-raising initiative
• Marketing Solar Thermal in different countries – Experiences from TISUN, an international company
• Solar Thermal as a marketing tool in developing specific forms of tourism
• Today’s technologies and markets
• State of the art combi-systems using solar thermal and wood pellets
• state of the art of collector solar thermal systems for multi-family houses
• Mainstreaming Solar down-under
• USA: Awaiting the solar thermal boom
• Japan: new policies to spark growth
• China: High growth in the world’s biggest solar thermal market
• Improving the quality of installations: The role of Qualite NR in France
• Trained for growth: THe state of training and education in german-speaking countries
• Teaching solar thermal system design using the Educational package POLYSUN.
• The state of the art of solar assisted cooling
• Energy performance assessment of solar-assisted dessicant cooling systems
• IDentification of most promising solar heating and cooling systems for market entry
• Germany: Developments in EUrope’s lead markets
• France: towards the widespread use of solar thermal
• Spain: Perspectives beyond solar obligations
• Italy: Opportunities and Threats in a high-opportunity market
• Sweden: Experiences from a smaller market
• European certification and labelling
• International standards for Solar water heaters (also by Ken Guthrie from Sustainability Victoria)
• Glazed air collectors: Draft for an extension of EN12875
• Reduction of Solar Keymark testing efforts by means of an extrapolation procedure for factory-made systems
• High Solar Fraction systems:
• COmbination solar thermal, heat pump and photovoltaic houses.  The zero-energy house
• Comparison of a geothermal PV and a solar-thermal system in terms of primary energy use
• The next generation of seasonal thermal energy storage systems
• Materials for compact thermal energy storage.
• Development of solar thermal industry in Tunisia and Northern Africa.
• Quality Assurance
• Telesuiweb – an innovative website for performance monitoring of individual and collective solar domestic HWS.
• Development of a reference framework for a Belgian quality scheme.
• Industrial processes and district heating
• Solar district heating in Europe
• Expert-system for supply of solar thermal energy in Industry
• Direct steam production in a concentrating Fresnel collector (Mirroxx)
• High-performance PCM-graphite heat storage systems for solar process heat
• The future of the solar thermal market – getting ready for the global boom
• Poster presentations including techno-economic evaluation of solar-assisted desalination systems in Europe
• SOLAIR – Increasing the market implementation of solar air-conditioning systems for small and medium applications in residential and commercial buildings.
• Development of a quick performance check procedure for solar thermal collectors.
• Solar Keymark – a review of 6 years of testing and inspection.

Came across a very promising local company here in Adelaide actively marketing solar lighting to councils and helping them to save power.  They have a virtually indestructible mushroom light on stainless bollards which many councils are putting in to their parks.

Link: www.sovereignsolar.com.au

The benefits of these types of lights are a no-brainer.  They don’t require 240V cabling so are installed easily without an electrician.  They are the solution for difficult-to-reach places where a trench is a problem.

The website suggests they are also extremely vandal-proof.  I imagine that’s a requirement for any municipal asset surely.

Apparently savings are over $1000 per bollard over a 5-year period.

Daily I have to delete handfuls of spam users (mostly from the .ru domain) and I am mighty tired of it.  From now on, if anyone wants to register as a contributor, then please email me on the obvious address a l e x . f i e d l e r @ s o l a r h o m e . c o m . a u

I have also performed a cleanup of old users.  If you have been inadvertently deleted, please let me know.

We should summarise what we know from a South Australian perspective about solar rebates for solar PV, solar hot water and building efficiency.  The federal government has some rebates and incentives available, instituted under the previous government.  The new federal government has promised some more emphasis but at the moment they are still just that, promises.

Solar Photovoltaics

The federal government rebate for the installation of photovoltaic panels and grid-connected inverters continues to gain in popularity.  Retailers are offering 1050W (rated) installations for $5000 and an $8000 subsidy applies.

The federal government is also subsidising the photovoltaic industry in other ways, with industry subsidies.  These help to make investment in this industry attractive.  Also the various academic programs in PV are funded through the national research council.

(Here we really should get the government to make some statements by way of a media release)

Solar Hot Water

The solar hot water systems for rooftop installations in domestic settings, havelong been subsidised in the country.  The subsidies are calculated based on renewable energy credits available depending on system size and efficiency.  They are designed to reflect the greenhouse gas saving.  The true effect is not easy to see, as this calculation does not take into account the method of heating that is being replaced.