Thread: Future of the Australian Electricity Market

Originally Posted by Mr Brush

Our Sanden heat pump HWS is programmed on the unit to only run between 10.00am and 3pm, when we're likely to have plenty of solar available. It only draws 900W, is almost completely silent, and only runs for a couple of hours anyway to provide enough hot water for a household of 2. Some days it doesn't need to run at all. Massive saving in running costs over a traditional electric hot water service.

If you don't mind me asking, have you measured how much power it draws in winter? The efficiency of (heating) heat pumps drops with decreasing ambient temperature, and whilst when investigating them I frequently saw specs quoting power draw at upwards of 30C ambient and fairly warm "cold water" temperatures, I'm intrigued as to what they draw in cooler conditions. In Canberra the summer average max is 27C, and in winter 12C (roughly speaking), so for the vast majority of the time such a unit would be operating at ambient and water temperatures far below those at which the spec is quoted. I assume the decrease in efficiency at lower temperatures is why the specs of heat pumps often also show a "max draw" which can be three times what they quote at >30C.

I've seen studies of heat pumps at lower temperatures, down to -10C or so, but they often seem to use "low temperature" heat pumps specifically designed for the job. Such "low temperature" heat pumps go from a COP of >4.5 at higher temperatures down to <3 at approaching 0C. I'd love to know how a real-life unit performs!

I chose the Sanden unit because it is one of the few on the market that uses a CO2 refrigerant, meaning it works better than most at low temperatures. I'm in the southern highlands, so similar to Canberra climate. The rated COP for the Sanden is 5.96 tested against the relevant AUS/NZ standards. The 900W I mentioned is in winter, when it rarely runs for more than 2-3 hours. In summer power consumption seems much the same (maybe 50W less), but it runs for noticeably shorter time. We had a Quantum heat pump HWS before the house was lost in bushfires of 3 years ago, but upgraded to the Sanden for the rebuild. The Quantum was much noisier (compressor integrated onto the top of the tank), while for the Sanden we have the separate compressor unit in an outdoors undercover services area with the tank on the other side of a wall inside the garage. The original Quantum HWS lived inside the garage too, but in recent years they changed to an inflammable refrigerant so the whole tank has to go outside.

Originally Posted by koshari

to their defense i don't think the electorate is very wise at all. this is a flaw with democracy, a fools vote is equal to the value of a savvy voter. and if you ever feel the need to underestimate the amount of fools in society just spend a bit of time at a boatramp or airport baggage carousel. you will be promptly reminded of the enormity of this demographic.

never mind going out of your way to a boat ramp or baggage carousel, You will get all the reminders you need on the road on the way there.

Reminds me of this

do you know how stupid the average person is?? #rickygervais - YouTube

Many a true word, etc....

Originally Posted by Warb

If you don't mind me asking, have you measured how much power it draws in winter? The efficiency of (heating) heat pumps drops with decreasing ambient temperature, and whilst when investigating them I frequently saw specs quoting power draw at upwards of 30C ambient and fairly warm "cold water" temperatures, I'm intrigued as to what they draw in cooler conditions. In Canberra the summer average max is 27C, and in winter 12C (roughly speaking), so for the vast majority of the time such a unit would be operating at ambient and water temperatures far below those at which the spec is quoted. I assume the decrease in efficiency at lower temperatures is why the specs of heat pumps often also show a "max draw" which can be three times what they quote at >30C.

I've seen studies of heat pumps at lower temperatures, down to -10C or so, but they often seem to use "low temperature" heat pumps specifically designed for the job. Such "low temperature" heat pumps go from a COP of >4.5 at higher temperatures down to <3 at approaching 0C. I'd love to know how a real-life unit performs!

We chose the Sanden because no matter what part of the system I was studying, the Sanden came out on top. We had already decided to get a heat pump system having discarded various other methods of using solar either directly or indirectly via our existing photo voltaic panels on the rooftops. The real question was, which one?

The Sanden unit does not consume greater or lesser amounts of power according to the ambient water temperature, nor the ambient air temperature. Basically it consumes around 880-890W. When it is operating the draw hovers between just under 900W and never below 870W. This is real time power consumption, from observations of our house system which runs everything through our house batteries, which in long daylight times are completely charged from our rooftop PV cells.

When the water temperature is colder, the pump runs longer, when the ambient temperature is cooler, the pump runs longer, and when either or both of those parameters are warmer, everything happens more expediently. Our system is set to run from 12:30 hours through to 19:00 hours daily. The timing is set for these times to allow the batteries to get some charge after their full or partial overnight depletion and hopefully by that time the sunlight is in full swing and we have excess power to run the HWS compressor. We have had our Sanden HWS in operation for 1¾ years, at times we've had 4 people in the house and the youngies somehow just suck up hot water, but we've never even looked like running out of hot water.

Tank size is important, ours is 301 litres. Speaking of tanks, the Sanden stainless steel tank is manufactured in Moorabbin by Aquamax, I know this for two reasons, one, I asked Sanden in Sydney, two, I have a brother who works for Aquamax in Moorabbin.

The system has it's temperature sensor in the middle of the tank, the system heats the tank to 63ºC, the system automatically mixes cold water with the outgoing hot water to get to the legal maximum, which I believe to be 50ºC, or something like that.

You should never switch the Sanden unit off, even when you are going away. Firstly any programming of when the system is allowed to work, is lost. Secondly, if the external temperature drops very low, the system detects this and starts the cycle to ensure it doesn't freeze up. As this will normally happen overnight and mostly pre-dawn as the minimum daily temperature happens, if you are running it from an off grid situation, you will need to ensure there is enough battery power to run the unit.

When our unit was first switched on, the temperature of the water going in was around 15ºC, the unit operated for around 4 hours before it switched off. Currently the unit is on for close to two hours daily, in warmer months I have seen it running for under one hour. I can monitor the run times from readouts on our house solar and battery system, they are accurate times.

The Sanden compressor is virtually silent, basically you need to be about 3-4 metres away before you can hear it and then when it you are standing alongside, unless there is not much background noise you can hear it. The Sanden compressor unit is also vibrationless free, or at least as vibration free as any of these can be. Ours is attached to our external brick wall underneath the bathroom window, it cannot be heard or felt in the bathroom.

One small issue for some people, is the water pressure. The Sanden system requires reasonably low water pressure, so you won't get a blasting water massage with these.

There are various tank sizes available, get the largest you can fit or afford; having a critical mass of water works in your favour with heat retention.

We spent all of July away this year, the Sanden HWS ran for under one hour daily, mostly around 40 minutes. I can go down to five minute intervals on the records. Now that we are back home, it is running for close to two hours a day. I just checked todays figures, it ran for about 95 minutes.

Mick.

Well, that explains why I can hardly detect any change in power drawn by the Sanden.

It really is a very impressive product, and that's us coming from another brand so we've had heat pump HWS of one kind or another for about 20 years now. Even our old Quantum unit gave a massive saving in power costs over conventional electric HWS, and the Sanden is better again. I don't have the battery considerations that you have, so just set it to only run when we generally have plenty of solar (4-5kW). Your experience with run times lines up with what we're seeing too.

Im back to interject with a "yeah, but more technology!"

Not a battery this time, but a CO2 to Propane tech..... neato!

Read up chaps and chapettes .... imagine what could be done with this tech on a farm ,or in industry....

Illinois Tech Engineer Spearheads Research Leading to Groundbreaking Green Propane Production Method | Illinois Institute of Technology

Asadi_Science_paper_1280x850.jpg

Originally Posted by Optimark

You should never switch the Sanden unit off, even when you are going away. Firstly any programming of when the system is allowed to work, is lost. Secondly, if the external temperature drops very low, the system detects this and starts the cycle to ensure it doesn't freeze up. As this will normally happen overnight and mostly pre-dawn as the minimum daily temperature happens, if you are running it from an off grid situation, you will need to ensure there is enough battery power to run the unit.

There's no battery back-up on its internal clock and settings? I wonder why not? It seems like a serious omission. Sanden are advertising a new WiFi controller and phone app, perhaps it removes the problem?

I saw mention of the low temperature cycling in the FAQ on the Sanden web page. It says "Please note that in cold climate regions, the Heat Pump unit will run during the night when the ambient temperature drops below 3oC. If used in an off-grid system, please ensure that adequate power is available", but it gives no further details. Do you know to what extent it runs? Are we looking at sporadically running a circulation pump to push hot water around the system, or significant usage of power - the phrase "the Heat Pump unit will run during the night when the ambient temperature drops below 3oC" could mean anything from an occasional buzz to 100% of the time! In the winter here it can be 3C and below for >14 hours a day.

Water pressure shouldn't be an issue - the Sanden specs says 850kPa maximum for the heat pump, and 500kPa inlet pressure to the tank. That's the standard domestic pressure, and higher than any normal domestic water pump (tank water) that I've used.

Warb, I lifted this from another thread I participated in when I was doing background information on the Sanden HWS.

Gas HWS or Heat Pump HWS


I also heard about the units coming on in the middle of the night in winter when it is cold and in some instances staying on for quite some time. This is true, but with the current G4 unit there is a defrost function which is tripped when the ambient goes below 3ºC and the unit goes into preservation by having a defrost for about 10 minutes to raise the compressor/heat exchange unit to 45ºC.

I asked about whether it was a good idea to turn the unit off on really cold nights, as in Melbourne on the few nights it gets down to around 1ºC or thereabouts? The answer was a definite no, the pipes in the compressor may freeze and then they may burst; it may be a quite expensive way to save a dollar or two. The same applies for when one goes away on a holiday in winter; leave the HWS on.

Mick.

Originally Posted by Optimark

We spent all of July away this year, the Sanden HWS ran for under one hour daily, mostly around 40 minutes. I can go down to five minute intervals on the records. Now that we are back home, it is running for close to two hours a day. I just checked todays figures, it ran for about 95 minutes.

Good feedback.
I'm betting you could get an even better result by wrapping the tank in batts and sisalation. I've done this to a standard HWS thats only timed to switch on btwn 12pm to 4pm to maximise solar usage.
Found that in the morning during winter the water was barely luke warm after not having an active heating element for 15 hours.
So it dropped approx 13 degrees overnight and wrapping the tank in batts, drops 2 degrees. My 2 tanks are out of the weather (shed and veranda)
Had the batts and siso lying around, so good "free" fix.

Originally Posted by Bart1080

I'm betting you could get an even better result by wrapping the tank in batts and sisalation.

It might depend on how old/cheap your hot water tank is. When I was young (in the UK), hot water tanks were uninsulated. Then the hardware stores started selling insulation kits specifically for (indoor) copper tanks. Then tanks started being sold with foam insulation covering most of their surface. These days, in Australia, tanks are covered by MEPS, so a new tank should be fairly well insulated off the shelf.

What can also make a difference is insulating the pipes, ideally all the way to the tap, but at least enough to stop them draining heat from the tank. I've also seen a device that insulates the relief valve without impacting its function, and whilst still allowing easy access for testing. Obviously a wad of rockwool would insulate the valve just as well, but care must be taken to avoid interfering with the valve or making it difficult to test.

Lastly, I encourage my family to wash their hands from the cold tap*. Washing hands in hot water involves either flushing an entire pipe-length of cold water down the drain waiting for the hot to arrive, or washing in cold water from the hot tap, and then letting the hot water cool in the pipes. Both are wasteful of either water or energy or both.

*Living on tank water through droughts, you learn not to waste! In my last house, I incorporated a hot water recirculation system that was activated by a switch near each outlet, and which circulated hot water from the tank outlet around the house and back to the inlet, switching off automatically when it detected that the water in the pipe was hot. When used with insulated pipes, this almost entirely removes wastage of water waiting for the hot to arrive.

Originally Posted by Warb

It might depend on how old/cheap your hot water tank is. When I was young (in the UK), hot water tanks were uninsulated. ... These days, in Australia, tanks are covered by MEPS, so a new tank should be fairly well insulated off the shelf. ...

What you say is undoubtedly true, Warb, but I am not sure that it is sufficient.

The average Australian home uses 23% of its energy consumption to heat water. A large portion of that heat is lost during the storage phase.
Access Denied
I know, two weaknesses with that data:

• Its from a government source, and
• You and I are not "average".

Most storage hot water systems seem to cycle on for 3-4 hours per day, meaning that they are in heat mode for 4 hours per day and radiating mode for 20 hours per day - implying that about 20/24ths of the energy is radiated - roughly 19% of the houses energy consumption.

It also says that for an "average" insulated house in winter between 25-35% of heat losses are through the ceiling.
Access Denied

Putting together those two wasters of heat:

• 19% - storage hot water system,
• 25-35% - ceiling radiation.
• Variance - 54-76%.

Summary: The HWS wastes half to three quarters as much energy as the ceiling.

Conclusion: Additional insulation of HWS is extremely cost effective. Just compare surface area of HWS to that of ceiling.

Originally Posted by Bart1080

Good feedback.
I'm betting you could get an even better result by wrapping the tank in batts and sisalation. I've done this to a standard HWS thats only timed to switch on btwn 12pm to 4pm to maximise solar usage.
Found that in the morning during winter the water was barely luke warm after not having an active heating element for 15 hours.
So it dropped approx 13 degrees overnight and wrapping the tank in batts, drops 2 degrees. My 2 tanks are out of the weather (shed and veranda)
Had the batts and siso lying around, so good "free" fix.

In our house, there is almost always a shower taken around 22:00, the next major lot of hot water is in the morning when I come back from the gym around 07:15 and have a shower. There has always been plenty of hot water and when we had four adults, two oldies and two youngies, we also never even looked like running out of hot water, even with the two youngies having a shower before going to work and before I have my return from the gym shower.

Our Sanden HWS has been programmed to only heat water between 12:30 and 19:00, so all showers are taken when the HWS cannot re-heat. The re-heating time in every 24 hour period is 6.5 hours. Everything is very well insulated, especially the external hot water piping. Basically our HWS has one heating cycle in that 6.5 hour period. I have no doubt if we wasted hot water, or had a higher usage pattern, it would come on again, but the reality is; it doesn't.

Mick.

HWS_001.jpgHWS_002.jpg

Originally Posted by GraemeCook

Most storage hot water systems seem to cycle on for 3-4 hours per day, meaning that they are in heat mode for 4 hours per day and radiating mode for 20 hours per day - implying that about 20/24ths of the energy is radiated - roughly 19% of the houses energy consumption.

Your first link says "About 30% of the energy used to heat water in a storage system is wasted in heat loss from the tank and associated pipework". I'd believe that, but keep in mind that's not all from the tank. As I said above, if you use hot water (or even just the hot tap) to wash your hands, all the hot water in the pipe cools down when you switch off the tap. Ever wondered how many times an "average" person runs a tap until the water gets hot, then switches it off 5 seconds later? That's a lot of heat being dissipated through the pipes!

Additionally, if Joe Average uses 200L per day, and (from a mixture of data sources) 30 to 40% of that is in the shower, that's 80L of water being heated to 42C (or thereabouts) every day. I have no idea whether it's accurate, but this calculator suggests 2.8kWh to heat 80L of water from 12C to 42C, which takes 46 minutes. That's just for one person's daily "average" shower requirement!

The last point is that all these statistics, if accurate at all, are "averages". That means they include both new (supposedly) efficient houses, and also places that are still using very old installations. It should. I suppose, be easy enough to check. If the outside of the tank is cool, the insulation is working. If it's warm or hot, the tank is leaking heat. I should go and find my non-contact thermometer!

Like most things, there's a great deal of "habit" about water and energy. For example, Sydney Water states that each person in Sydney uses 200L of water PER DAY. People who are used to living on tank (rain) water would find that almost unbelievable. But it's an easy habit to get in to. My kids had 5 minute showers when they lived at home. A couple of years of living in cities and they regard showers as a place to relax - 15 minutes is a "quick" shower! My mothers-in-law's apartment has the water heater (seemingly) in a building down the street; you turn on the hot in the shower, then make coffee and read the paper, then go back and check to see if the hot has arrived! In that apartment, every time hot water reaches an outlet, I'd guess that the power to heat >15L or so of water is wasted as the pipes cool back down.