You're right, I have installed a solar system few years ago and this fact actually enabled me to remodel the whole house. I only finished the process few months ago when I got a new bathroom accessories set, I don't think I will be able to go with a new different system now...

However, the primary need for central heating is at night and in winter when solar gain is lower. Therefore, solar water heating for washing and bathing is often a better application than central heating because supply and demand are better matched. Thanks. Regards, reverse phone lookup

One thing that really annoys me is the complete lack of an intelligent control system on all in-tank boosted solar HW systems. As good as heat-pump boosting is you could probably save at least the same number of kwh if you knew the temp of the water in the tank and could intelligently optimise the boost time to give you exactly the 100 litres or whatever you need to get your through the morning. Has anyone come across a suitable control system?

Hi Matt - love your stuff.  On the point however about whether or not solar hot water is green, unfortunately any green impact that individuals think they are making by installing domestic systems are wiped out by the policy desicion to include these technologies in the Renewable Energy market.  With the target for REC production fixed by target and Greenpower sales, one solar installation simply offsets another.  Even worse, until recently REC multipliers on solar PV actually offset up to 5 times the amount of green energy that they prouced, a signficant net increase in carbon emissions as it removed the need for commercial installations.  This is the reason for the current glut of RECs in the market and hibernation of the wind industry.  Sorry - sad but true.  Best way to be green in this policy environment is efficiency and/or buy Greenpower.  Agree?

Matthew,

We are in agreement, I think, that the low efficiency of photosynthesis will limit the role of biomass energy. However, a number of important niches are likely to remain. The use of waste biomass is likely to be one of the most important, particularly processes (such as biochar production from pyrolysis) which contribute carbon sequestration. At least two biomass processes (biogas from human and animal wastes, slow pyrolysis of green wastes) have waste management benefits.

I have a question for you: apart from solar thermal, what future arrangements do you envisage for raising steam?

Finally, I wrote an article about my German boiler in ReNew 116 for those that are interested.

The land use for heat pump boosted solar hot water powered by a wind turbine is something like 40 upto 80 times more efficient than burning biomass for the same thing at 53% average efficiency.  So even if you are 92% efficient that would still be at least 20x the land area.  And land competition is a big deal when you want to preserve biodiversity and feed 7Billion people growing to 9 Billion by 2050

David,

I can't comment on your particular case without more information. But for the bulk of the public, I would argue most of the people who have a reliable connection to the electricity system an evacuated tube system boosted by a heat pump or a straight heat pump is the most efficient thing to do.

That is not to make anyone feel guilty about their existing setup. Which would be based on the information they had at the time.

 My setup until now has been gas boosted solar hot water.  Thanks to Edson for bringing out the heat pump boosted solar hot water heater, I can now have an all electric house with a very efficient water heating system.

Basically what we generally are talking about is how to power the bulk of the population that live in cities and towns (say 95% +)  I think in our buildings plan modelling (I have to confirm tomorrow) we are showing a flat lining of wood use but no growth while gas goes down to zero and renewable ambient heat and solar grows to complete coverage of all but wood.

For the bulk of people wood also includes embodied transportation.

Matthew, I usually agree with you, but the sweeping generalization of your comment about burning wood requires a response. Sometime the use of wood as a fuel is inappropriate and it can be burned very inefficiently; but the converse is also true. I my case I live on around 60 ha in Northern Tasmania, with plantation tree growing the major activity. Even before a wind storm blew over enough trees to provide many years' worth of firewood, wastes arising from the plantations supplied all my firewood.

I burn my wood in an advanced wood fired boiler I imported from Germany. The boiler heats the house and boosts my evacuated tube SHWS via a heat store which allows the boiler to run in batch mode. The boiler has automatic ignition so it will fire up when the heat store is low. The manufacturer claims 92% efficiency for his boilers, and my qualitative experience does not contradict that claim.

It is easy to form an incorrect impression about the efficiency of burning wood in Australia when the standard of the technology usually employed to do it here is so low.

It's not economic to design zero boost.  It is cheaper to have a small pump doing additional boosting (heat pump) and build a decent sized system, that to expend a stupid amount of resource making it too big

I note that you have a water jacket on a wood stove.  Wood is the most shocking, inefficent method of heating around.  It takes 80 times the land area (worse in some instances) to heat with wood than to use a wind turbine combined with a heat pump.  Similar result for cooking with wood.  It seems your system is terribly sub optimal and should be replaced immediately with induction cooktops and a solar boosted heat pump hot water service and reverse cycle air conditioning.

Burning wood is one of the most inefficient things someone can do in their life.

Sorry, I disagree.  It's ALWAYS possible to design for zero boost, it might just require "more resources", like a bigger tank, more panels/tubes, but it is always possible.

What's really required is the will to do it.

Oh and if you do on rare occasions run out of steamy hot water, is it the end of the world?

J Cooper

In locations servicing most of the country the units will perform annually at higher than COP3 however the peak operating condition on cold days is what counts.

We would take a conservative estimate of COP in our modelling, in peak conditions (coldest winter days) based on real world performance.  So we would derate the COP.   The smarts required to switch on and off hot water from the head end (Grid operator) are already built into the smart meters being rolled out in Victoria, and will at a minimum be in the specification of smart meters overseas.  The evening does not offer the worst COP, the coldest period in most locations is the morning.

Additionally the huge amount of money saved by rippping up the gas network would allow us to roll some of that money saved into the electricity network.  So if any grid upgrades are required to handle this, then they are paid for by money that was previously spent on gas and the gas network.

Switching electric resistive to heat pumps is a non brainer at the same time of switching gas to heat pumps.  Again it does not matter if there is some level of upgrade required to the electricity grid as we're winning in productivity terms because we're no longer servicing a redundant inferior energy network (the gas network).

Test conditions are without wind and the air flow allowed in the installation manual.  Windy conditions improve the performance of a reverse cycle air conditioner.

While modelling is useful, real world stats can sometimes differ. Eg will the Edson be COP=3 for the life of the system, ie when the grille is covered with spiderwebs and the rats have made their nests in it? What about different installation positions, eg Southern side of building, windy area, coastal vs inland. Real data needs to be considered!

re "change to heat pumps we are able to phase out and shutdown the domestic gas network which allows us to roll the money wasted on this" To shut down existing infrastructure and building/upgrading involves a lot of Co2 production, do you add that to your modelling?

Your article talked about replacing a gas HWS with heat pump, then to justify not increasing peak demand in your reply you say swapping resistive heaters to heat pump. They are 2 different equations. Gas to heat pump increases peak electricity demand until we have an intelligent grid which tells the heatpumps to have a rest. Oh, yet another upgrade costing more and more $. Its an endless cycle.

Mike,

Some places in Australia will not need boosting. But if that covers 2 million people for hot water out of a population of 22 million, what system do we implement for the other 20 million people?

The answer is heat pumps, because the cost of resistive boosting + grid sizing is more than the cost of heat pumps + grid sizing.

If there is zero requirement for boosting then do not supply and install a resistive element with the solar system. (and ban wood in on grid locations)

If you lived in Sydney, Melbourne, Adelaide or Perth you would have cold water if you didn't have boosting.

We live on the Sunshine Coast QLD.  In seven years, we have NEVER boosted.  It's all about efficient installation.

We have just got a 50~60 yr old combustion stove going, and its wetback is connected to our storage tank, so now when it's cloudy, we have just as much HW as we ever do, and that is LOADS!

http://damnthematrix.wordpress.com/2011/09/04/the-power-of-energy-effici...

J Cooper,

Even on cloudy days there is some solar gain (not insignificant) into evacuated tubes.  During cloudy days temperatures are often higher.

Boosting in the evening is fine, if you look at where the bulk of the Australian population lives, evenings are not that cool and heat pumps such as Edson's will be running at C.O.P 3 average across a period like this.  That's because we're talking about the boosting that is happening in Melbourne, Adelaide, Sydney, Newcastle, Wollongong, Canberra, Brisbane - the areas where the bulk of the population lies.   We are doing modelling to show this as part of the Zero Carbon Australia Buildings plan. 

So by using heat pumps we only need to provision one third of the generating capacity on the back end of what we would have to if we were to use electric resisters to heat.  

By making the change to heat pumps we are able to phase out and shutdown the domestic gas network which allows us to roll the money wasted on this inferior obsolete energy network into improving the electricity network while pocketing a saving from the efficiency gain.

By targetting existing electric resistive heaters, space and water (we need incentives / regulation for landlords here as well) We can significantly reduce peak winter demand which frees up a lot of the capacity required for the new heat pumps that are fuel switching from gas.

Perth - scarcely need a booster for the solar hws. Need to put shadecloth on the collector in the summer!

Small's SolaKleen, installed 1983, expected lifetime 40 years.
Boosted from the lounge fire (which runs on waste wood,
and we need it every evening in the old house with high ceilings).
The electric booster has a readily accessible switch near the bathroom, and the booster heats only a small part of the top of the tank.
Bills (including Seniors Discount on standing charge - but there is none on consumption) are $18 per month for electricity for the whole house (I guess it is the fridge), and
average of $18 per month on gas (but with huge seasonal variations in the gas bill -essentially nothing in summer).

Oh - in Mar 2010 parts of Perth suffered a massive hail storm - and the glass of older solar hws (including ours) got broken but new solar hws, with thicker glass, didn't. The $800 repair bill (only half on insurance) messed up the economics of our solar hws!

Solar hws are OK.  Ye olde passive flat plate versions have nothing much to go wrong (just corrosion over time). Might not be perfect, but some of us like them.

During an extended cloudy winter period, a heat pump may need to operate for 6-10hrs/day to heat your water, and this will probably overlap with peak power demand.

The only way to overcome this clash would be to have the heat pump on an off-peak tariff meaning running it at the worst ambient temperatures. I'd like to see some real-world stats on these solutions rather than just sales brochure figures.

Also, the use of heat pump SHW may save carbon emissions, but you are paying say 25c/kWh vs 9c, even worse on TOU tariffs you might be paying 50c/kWh instead of 9c to heat the water so it might end up having higher running costs.

We are in Brisbane and our electric boosted evacuated tube solar hot water system has the booster switched on in the middle of May and switched off by the end of July except for the occasions when we have rain or overcast for 3 or more days for around 9 months a year our hot water is 100% solar including the small circulation pump which has its modest power demands provided by the solar PV panels on the roof along with up to 2 kW to neighbour's air conditioner by way of the grid.

The system I have is cheaper than most heating and cooling systems out there.

Many houses have an evaporative cooler which fully installed to mulitple points and zoned would be 4,000

Then the have a gas central heating system which could be as much as 7,000

To get gas into a new home costs thousands.

My system 6 units (in other words fully zoned) plant Panasonic 2.6kW cool / 3.6kW heat cost $650 x 6 = $3900

Installation was probably a bit high I paid $6400.  I believe installation should be available reasonably at half that price for back to back units.

The evacuated tubes and the heat pump are much cheaper than the cost of dangerous climate change.  That the cost of running two entire energy delivery networks when one of them is completely redundant (the gas one).  The heat pump boosted solar water option is cheaper all round.

More efficient to have heat pump and evacuated tubes.

If you want to choose one or the other then the answer is normally the heat pump.  The evacuated tubes prolong the life of the heat pump and take the onsite renewables portion up close to 90% or even above in some locations in australia.

There are some exceptions such as alpine regions which would be better with more expensive ground source heat pump options.

30% incline Edwards flat plate 3 collector system with 300litre Stainless tank in Melbourne. Rinnai type Edwards booster.

I bet you are not in Melbourne.

The manufacturing costs of the CO2 heat pump are much lower than the lifetime of using 3x as much energy from the electricity grid.

Also this stuff is recyclable / servicable AND as we decarbonise the grid the manufacturing of the heat pumps is zero emissions as well.

If we're not going to decarbonise the grid for supplying manufacturing we can throw the towel in now.

This is not about skimping on the size.  My system has 3 flat plate collectors which is a standard sizing for a 4 bedroom house.a shift to 4 collectors wouldn't have done much more for us, the problem is long extended cloudy periods in Melbourne and having the unit at 30degrees instead of 60 degrees incline to the horizontal.

Completely agree,  If you can get Solar PV, Heat Pumps (reverse cycle air conditionerse for space heating) Heat pump boosted solar hot water from a company  like Edson (where is the rest of the industry in offering this superior product?)  Get solar panels up on your roof if you can so you're a net energy exporter.  And most importantly, for any electricity being imported into your premises get a 100% renewable energy contract from your electricity retailer.

Such as 100% Wind or 100% Solar contract.

Hi Matt,

You are not correct with what you're saying here.  There is heat in the air at any temperature above absolute zero.  With an evacuated tube solar system boosted by a heat pump such as Edson's unit, you are collecting solar energy directly via the evac tubes during the day, then in the evening when the temperature is say 10 or 15C outside (Melbourne example and even better in Sydney type climate) then the unit is running at COP 3 or 4 putting heat stored in the outside environment into the tank bringing the temperature up.

Although my gas boosted solar hot water unit was installed with an instantaneous booster, (I specified it that way at the time) many units on the market such as my parents still use a storage tank with gas boosting the solar preheated water in the tank. 

John,

In Australia it is common to find instantaneous gas boosted solar hot water, (as I have had for 10 years) and storage tank gas hot water (as my parents have) where the gas comes on with a timer to boost the water in the storage tank.

In Japan CO2 Eco-cute units from Hitachi and other manufacturers do instantaneous heat pump hot water with decent C.O.Ps.

No gas boosted system in Melbourne offers 10% offsite 90% onsite renewable generation.  Only heat pump boosted evacuated tube hot water offers this.

My gas boosted solar (an older unit from Edwards) gives about 65% solar contribution, has a huge electrical parasite for the controller (comes out of the same factoris as the Rinnai units).  While an Edson Heat pump boosted solar will give 85-90% Direct Solar (evac tubes) and indirect Solar (renewable ambient heat).

Gas produces more CO2 than electricity, as the electricity transitionally can be purchased as green power until we completey decarbonise the electricity grid, which is coming as per the Germans and Spanish paving the way with their respective massive rollouts of renewables.

Chris,

If you start to get high penetration of Electric boosted solar hot water systems and then you take into account the cost of sizing the grid to meet the peak boosting requirement then boosting at 1/3 of the real time energy demand per installation through the most difficult cool cloud covered periods of winter is much cheaper than sizing the grid and building renewable generation for winter.

It's a distortion that it appears better value to you to install an electric resistive element boost than a more expensive heat pump boost.  The overall system cost - network (distribution network /transmission network) + extra peaking generation on the back end is cheaper to install heat pump boosted solar than electric element boosted.  To fix this distortion adequate incentives should be set.

Leaving the heat pump aside for a moment, there is a big difference between gas-boosted solar systems, and electric-boosted ones.

Unless an elctric-boosted system is controlled by an isolation switch on the element, it will often be heating water in the tank unnecessarily. In a properly-sized system, the sun was going to reheat the cold water in the tank the next day . Having the booster come on overnight to heat the water means you spent energy when you didn't need to, and prevent the sun from doing it's job next day.

With a gas-boosted system, the gas burner only turns on when the tank runs out of hot water. In effect, it's a 'booster of last resort'. As long as the sdun can do the job, the booster doesn't come on. As a result, gas-boosted system generally provide a higher percentage of solar contribution. Gas also costs less, and produces less CO2, than electricity does to produce the same amount of hot water.

Our company has sold both heat pump hot water systems, and evacuated tube systems, since 2005. We look forward to this hybrid product, and it's brother under another brand name.

I guess you can patch-up an undersized solar system with a heat pump but why bother? The extra asset cost would be better spent on getting extra collectors or a bigger tank or both. I have a fundamental dislike of in-tank boosting systems, heatpump or otherwise, which are fundamentally inefficient and frequently over-boost. Heatpump boosting should be reserved for commercial applications where there is no gas.

@Matt Stagg:

You seem to be saying that the heat pump is running when it's not needed during the sunny part of the day. I don't think that's what Matt Wright was saying and I'd be very surprised if anyone designed a hot water booster that way.

The heat pump compresses ambient heat from the air, any time of the day - as the article points out, it should work OK even at 0°C (273°K) - there is still ambient heat.

Yes, it's less efficient than it would be in the middle of a hot day, but still markedly better than using a resistive element if the figures here are accurate.

And it's a shame that gas continues to be rolled out when we have these options. My mum in Hobart recently got gas connected and thought it was great. I'm sure the gas companies think it's great too! Shame in a state with abundant renewable energy.

·   

We have had Solar hot water for around 40 years. The first house ( for a family of 4) around 25 years  in Canberra was not subsidised and we reckoned that the panels were paid off in 2 years of electricity savings. It was still going when we left.  Now we live in Sydney and have  another, electrically boosted regular solar h/w system and it costs us less than $50 a year for an average of 8 people in the house per night! I would not believe we could do better. I would think it has paid for its self in 9 years? Joanna

There's another article on this site saying the UK is passing legislation that will allow minimum energy efficiency standards on all houses, including rentals. I would welcome this, even if it meant that I had to pay more rent. It would be offset by a reduced power bill. There is currently little or no incentive for landlords to improve energy independance of the houses they lease to tenants.