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Soon after writing the previous post on hydronic heating I came across a system which seems to me superior in a way which is  simple for the layman to understand.  This system is the thermalboard system ostensibly from the US.  This is basically aluminium-covered MDF board which has the tracks for the piping routed into it.  You simply screw it down and then tramp the piping into the tracks.  The Aluminium overhangs the tracks so when the piping is inserted, it naturally contacts the aluminium.  This system has the advantage of a smaller thermal mass and the heat-spreading characteristics of the aluminium means that the system is very responsive.  The website has several PDF documents which spell out the exact benefits.

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.

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.

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.

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.

Parts list:

(1) Round conventional fresnel lens of radius 100mm and focal length around 80mm.
(2) 3mm Aluminium plate cut into semicircle of inner radius 105mm and width 20mm
(3) 5mm Al, acrylic bronze or hardwood plate cut into semicircle of inner radius 115mm and width 25mm.
(4) thin steel spring of diameter 3.5mm of length such that elastic extension stretches around outer circumference of (2)

stretch and glue spring to the outer edge of (2). this becomes the thread.
attach (2) to (1) at right angles to the disc.
cut perpendicular 10mm slot 3mm wide, into the inner surface of (3) halfway along the length.
This will allow (2) to slot into (3).
Attach worm drive to (3) at the slot, and connect to the thread of (2).

Route a semicircular shape groove into the outer edge of (3) or diameter 3mm.
glue a thin steel spring into this groove, stretched to achieve the required pitch.

slide (3) into a rectangular collar (4) and attach a worm drive to the spring thread.

I have observed many readers agonising over how large to make their system, and how much to spend on it. It seems to be difficult, but why?

Estimating the annual hot water output of any given system, in kWh per annum, is not difficult. I can get a collector, storage tank, booster system, and known pipe run with insulation of a known grade, pump water at a known flow rate and know the output temperature for a given Australian location. It is a model with known inputs, and known behaviour.

Yet the question of how large to make the system, and how to design it, is still incredibly challenging. It takes time, and much research on the part of the consumer, and their consultant.

So where is the difficulty?

It turns out the hardest part is discovering what YOU want, and what your needs are. How much hot water do you need? When do you need it? How much fossil energy do you wish to replace, and what is it worth to you?

Some people want 100% of their hot water from solar. Even with a six member household, the morning after a cold winter day. It is definitely possible.

Others just want to get the absolute quickest payback period on their investment. They know they have to store & boost, and they can easily achieve a 6 year payback period.

The question everyone is asking is this: is the fastest payback always the most cost-efficient investment? It turns out that it is.

Let’s compare two scenarios, where the payback is the same, but the outlay is different.

Scenario 1: Householder pays $2000 (additional cost over and above the cost of a non-solar replacement system). Say this system saves $800 per year. Note the payback is not 5 years, but 9 years, assuming an 8% cost of money. The net present value of those savings over a 20-year system life is $7854. Therefore the householder has saved $3854.

Scenario 2: Householder pays $6000 and saves $1000 per year. The payback is still 9 years. the net present value of those savings over the system life is now 9818. But we notice the householder has saved roughly the same $3818.

On the basis of these considerations, the householder should make the smaller investment.

Now we have gotten a little closer to a good decision. If I can calculate the system output, and calculate the cost savings, then I can calculate the payback period. The assumptions may not be perfect, but it’s fair to say that the shortest payback period wins anyway, no matter what the assumptions are. Much of this has to do with the fact that the future is uncertain, and the far future more so. People can and do, choose the system with the shortest payback period.

However not all people do that. Not even most of them. Not in this market anyway. The same way that not all people drive the smallest possible car, or live in the cheapest possible neighbourhood. Some people still opt for maximum self-reliance. Why?

The reason, as for what car to drive, and what suburb to live in, is that the calculus is far more complex. These factors should not be called intangibles, for they are tangible to anyone making a decision. They are just not consciously considered. So let’s call them subliminals. They are rationales which appear subliminally in people’s calculations, and are not apparent in most cost-benefit analyses, unless these are truly sophisticated.

These are the same subliminals which will have enthusiasts spend tens of thousands more for a HSV edition of their favourite Commodore. Or buy a Ferrari, or spend tens of thousands on their childrens’ private education.

Subliminals like the anticipated increase in the cost of energy. Uncertainty about the future generally. Less reliance on a faceless utility. The repeated satisfaction of getting a small hot water bill. The cash-flow benefits of buying a money-saving device when times are good, to insure against when times are bad. The satisfaction of self-reliance. Pride. Contemplation of, and marvel at, the technology. Being reminded of the sun’s abundance. These considerations get rapidly more specious and fanciful and I’d better stop here.

So, having ascertained that the smallest investment is the most cost-effective (at least when using an Excel spreadsheet with two inputs), let’s go to the other extreme.

Let’s consider a system so large that I don’t even need a booster. Technically feasible, even when you consider the regulatory requirement for the water store to be above 60C just before use, to destroy legionella. With the new evacuated tube collectors, I can triple my normal collector size, and boil my water on a 10C day in the middle of winter. Does this change my equation? Actually I think it does.

So to any given system I now add two more collectors at $1000 each, and subtract a $1000 instant gas booster. And subtract a complete gas bill altogether. I haven’t done my sums but I can see immediately that there are some people for whom this would make perfect economic sense. This makes even more sense when the extra hot water is used for space heating or airconditioning, but we are speculating here…