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55 posts

Master Geek
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Topic # 242434 28-Oct-2018 15:50
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Has anybody used these Energie thermodynamic "solar" hot water panels. The supplier claims an 80% saving on hot water (assume compared to standard electric cylinder).

 

I dont know why they call them solar because to me they are just a different type of heat pump. But anyway would be interested if anybody has experience or feedback.

 

www.thealternativeenergycompany.co.nz

 

 

 

Cheers.


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Uber Geek
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  Reply # 2115455 28-Oct-2018 17:06
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It's a heat pump hot water system. It just doesn't use a regular outdoor unit.

I can see it being the tiniest bit more efficient than a regular heat pump system because it doesn't have a fan.
However, you are locked into their system. A regular heat pump water heater isn't tied to a manufacturer.

I also hope their video is inaccurate, I feel like you's get significant gains swapping the hot and cold lines at the tank




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  Reply # 2115460 28-Oct-2018 17:18
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andrewNZ: I can see it being the tiniest bit more efficient than a regular heat pump system because it doesn't have a fan.

 

Fans are used because they increase efficiency. Faster moving air has a higher rate of heat transfer. Normally the increase in energy transfer is much greater than the cost of running a fan.

 

In nature, wind chill is the same effect when air movement (wind) increases heat transfer out of our bodies.

 

A similar principle applies when pumping the fluid in solar hot water systems - active pumping is increases the rate of heat transfer over passive heat transfer that only relies on natural convection.


 
 
 
 




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Master Geek
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  Reply # 2115462 28-Oct-2018 17:24
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I guess a big question for me is what the COP is under 5 Deg C (in addition to the costs).

Perhaps the panels are less likely to freeze and need defrosting than a standard heatpump in very cold temps.


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  Reply # 2115709 29-Oct-2018 00:24
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The FAQ page says that it had a COP of 4.33 to 1. Yet it would need a 5 to 1 COP to achieve the claimed 80% energy savings. And no mention of what outdoor temperature that COP was measured at.

Maybe they are relying on the sun heating that panel to help achieve higher COP figures.





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  Reply # 2115712 29-Oct-2018 02:32
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Aredwood:
Maybe they are relying on the sun heating that panel to help achieve higher COP figures.

 

In their videos they show the panels placed on roof and angled towards the sun - both for houses and apartment buildings. Their copy tries to move the focus away from solar but their demonstrations show it.




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Master Geek
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  Reply # 2115782 29-Oct-2018 09:09
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So just to update on this thread on more info I got from them on the phone.

 

It is effectively a solar enhanced heatpump. So to get its higher COP, panel needs to be orientated like a PV panel. Typical equipment cost is higher than an air to water heat pump. For large family home indicative costs were 8-10k. They say payback period of 4-5 years.

 

I expect this would be a good solution for an install where you wanted both heatpump and solar for heating hot water, as this would effectively do both with one product set. 

 

Think the cost is just that bit to high at the moment, and as I dont have suitable north face to mount panels within reasonable distance of my HWC I will look at something else. Maybe standard cylinder with PV

 

 

 

 

 

 


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Ultimate Geek
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  Reply # 2115863 29-Oct-2018 10:07
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Hammerer: Fans are used because they increase efficiency. Faster moving air has a higher rate of heat transfer. Normally the increase in energy transfer is much greater than the cost of running a fan.

 

In nature, wind chill is the same effect when air movement (wind) increases heat transfer out of our bodies.

 

A similar principle applies when pumping the fluid in solar hot water systems - active pumping is increases the rate of heat transfer over passive heat transfer that only relies on natural convection.

 

You are right that the heat transfer is better when there is air movement, but if the evaporator is sized so that it doesn't need a fan then the electrical input is still reduced and the COP improved.  In these systems the solar panel is a direct expansion evaporator, so the panel can work fine at very low temperatures (like a normal heat pump) with the additional benefit of solar energy as a heat source.





McLean

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Wannabe Geek


  Reply # 2115994 29-Oct-2018 11:34
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Some interesting comments. Most people are correct, this is an air to water heat pump system. The difference is that instead of using a fan and a motor to drag air across the evaporator the Energie system uses a lightweight solar thermodynamic panel as its evaporator. This saves on the electricity required to drive the fan motor and removes numerous moving parts and the requirement to clean filters. The big difference is that the solar thermodynamic panel benefits from being exposed to the environment. Solar gain and the effects of rain (even snow) on the solar thermodynamic panel, which immediately transfer heat to the refrigerant, greatly enhance the system’s performance over that of a standard air to water heat pump (by about 35%). The Energie system uses a Danfoss compressor which normally uses about 400 W when running, the compressor only runs when it needs to heat the water.

 

Basically you are getting the benefits of an air to water heat pump system i.e. reliable hot water all year, without the associated noisy fan and maintenance issues, and the benefits of a traditional solar thermal system i.e. solar gain, without the associated freezing or boiling problems. It is a proven, reliable, maintenance free system with an expected life of 25 years, which should easily achieve the 80% savings claimed.

 

If you have any specific questions about this advanced Energie system we are keen to help.

 

Geoff Read, Director

 

The Alternative Energy Company

 

admin@taec.co.nz, 03 540 3003


neb

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Ultimate Geek
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  Reply # 2116189 29-Oct-2018 13:23
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Hammerer:

Fans are used because they increase efficiency. Faster moving air has a higher rate of heat transfer. Normally the increase in energy transfer is much greater than the cost of running a fan.

 

 

Yup. The difference between purely passively cooling (or in general heat transfer) and even the most pathetic air flow is enormous. As you get to larger quantities of heat to remove you have to work harder and harder, but adding even a tiny fan to get any amount of air movement over the cooling surface makes a big difference.

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Master Geek
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  Reply # 2116470 29-Oct-2018 20:36
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I was asked to look at this earlier in the year for a friend who was thinking of using it. (I'm a retired energy specialist.) Here is what I wrote, it's rather long, but includes a lot of detail.

 

Start looking at typical electric water costs (June 2018).

 

Use the EECA water heater calculator. For a 2 person house with 2 showers per day & 1 bath per week this gives a cost of $915/yr (calculated in June 2018) using electric immersion, but everyone is different. https://www.energywise.govt.nz/tools/water-heating/ (Which at the cost used in the calculator use is around 4,000 kWh/yr)

 

What are the realistic savings? What is the payback?

 

General consensus is moving away from SHW to photovoltaic direct heating, but I’m still a fan of SHW – for the moment. Although see reference for fairly old USA musings on this (6).

 

The “Thermodynamic Solar System” (TSS)

 

This is NOT a solar hot water heating panel. It is an air to water heat pump that works on temperature difference, enhanced by solar gain to the panel. That in itself is not an issue and the technology of heat pumps is sound, and maintenance of the TSS refrigerant part should be similar to that of a heat pump. There are plenty of air to water heat pumps around and they work fine in Oz but are generally are not recommended for NZ as they are not financially viable. The TSS does differ from a standard air to water heat pump in that it does not have a fan on the evaporator (the outside part they call a solar panel), so in theory it may be more efficient than a standard air to water heat pump as it drops one of the electricity consuming parts. In theory there will be a radiative gain to the evaporator panel, but the main driver is temperature difference between the panel and the ambient air. That is why it does not have a glass covering like a standard SHW panel.

 

As I always say with such things - show me the independent testing.

 

I found one source of data (1) in the UK  by NAREC and although I believe there are other test data around (2), I was not able to find them, and as stated “Test data exists for other countries with substantially different climates, but this information is of little value as being representative of UK conditions.”(1)  The same company NAREC (3) in the UK went on to test the TSS over six months. Test conditions in the UK will be similar to NZ although we have higher solar irradiance.

 

From the test results, average CoP in winter conditions were say 1.07 (1.50) and in early summer 1.6 (2.23). (Note. The first figure takes into account the standing heat loss from the cylinder and is the number you should use for all calculations. The second number in brackets () is the CoP if you exclude the heat loss from the cylinder and just look at the hot water draw off.) The CoP for Canterbury is likely to be slightly higher than the test results as the test was undertaken in Blyth North England.

 

Either way, the numbers are not good. The average of the data sets was 1.4 CoP. So in theory, given the EECA costs above it would save around $220/yr. It would have to be a very cheap system to warrant replacement on payback periods alone.

 

If I was installing it I would want a written guarantee of performance (within acceptable parameters). It will be interesting to see the quote.

 

Coefficient of Performance (CoP)

 

The CoP of an electric hot water heater is 1.0. By their nature heat pumps provide more energy than electricity they use to power them. As the TSS heats water to 55C, the CoP will be much lower than a standard air to air heat pump that we are familiar with. It is interesting that nowhere on the manufacturer’s website or literature do they state CoP, they only state max and medium “Thermal Power” and electrical “Power Consumption”. These and CoP are two very different things.

 

It is only on the supplier’s website that a CoP of 4.33 is stated (5). This is misleading as that is the max value in ideal conditions, it is NOT a value that should be used for seasonal averages or for working out expected consumption.

 

Test methodology. The NAREC website does not state their test methodology, just the results, but I notice in one photo they show a heat meter. I assume this is how water energy balances were obtained, but I obviously have no idea. As they have published the result I’m assuming they are correct as there seems to be no challenge to the results that I could find in a web search.

 

Maintenance. I have no knowledge as to the quality of the product, a quick search gave the normal high praise and heavy warnings. As stated above the refrigeration part of the system should be similar to a heat pump, but we have cheap ones and good ones. The cylinder itself has a magnesium sacrificial anode which will need periodic inspection and replacement. Other than that it seems pretty standard, the issue would be finding local companies to do the work. This can be a major issue as you found with your SHW system.

 

Freezing. All heat pumps will freeze up in winter conditions and will reverse cycle to melt the ice. No heat is available during this process. The TSS panel seems to load with ice which then melts when the compressor turns off as shown in a user video (4). This does not seem to be a defrost cycle as such. Limited energy will be extracted from a frozen panel  and this ALWAYS effects the overall COP.

 

     

  1. http://www.narecde.co.uk/thermodynamic-panel-data/
  2. http://www.narecde.co.uk/solar-thermodynamic-panels-independent-test-challenge-part-ii/
  3. “Narec Distributed Energy is a spin out company from the UK National Renewable Energy Centre. Narec Distributed Energy is an organisation which carries out a wide range of work within the renewable and low carbon sector, particularly within the built environment.” http://www.narecde.co.uk/about/
  4. Video of a Scottish installation from someone that seems relatively happy with the installation https://www.youtube.com/watch?v=HF2A7hBX8AY
  5. https://www.thealternativeenergycompany.co.nz/faqs
  6. http://www.greenbuildingadvisor.com/blogs/dept/musings/solar-thermal-really-really-dead

 

 


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Ultimate Geek
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  Reply # 2116670 30-Oct-2018 10:24
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MartinGZ: ….From the test results, average CoP in winter conditions were say 1.07 (1.50) and in early summer 1.6 (2.23). (Note. The first figure takes into account the standing heat loss from the cylinder and is the number you should use for all calculations. The second number in brackets () is the CoP if you exclude the heat loss from the cylinder and just look at the hot water draw off.) The CoP for Canterbury is likely to be slightly higher than the test results as the test was undertaken in Blyth North England.

 

Either way, the numbers are not good. The average of the data sets was 1.4 CoP. So in theory, given the EECA costs above it would save around $220/yr. It would have to be a very cheap system to warrant replacement on payback periods alone.

 

I'm not sure that's quite right. If the standing loss is included then the CoP is the HIGHER of the two numbers, not the lower.  So the average CoP for the year was about 2.0 if you're assessing the input energy cost saving.

 

But it still doesn't make the payback work.

 

It would be good to know how the "solar" one compares with a conventional hot water heat pump (with a finned-coil evaporator). Manufacturers of these vaguely suggest a much higher CoP, but I suspect if both were tested under the same regime the "solar" one may do better.





McLean

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Master Geek
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  Reply # 2117257 31-Oct-2018 09:30
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mclean:

 

I'm not sure that's quite right. If the standing loss is included then the CoP is the HIGHER of the two numbers, not the lower.  So the average CoP for the year was about 2.0 if you're assessing the input energy cost saving.

 

 

Sorry, you are correct for the general case if you use things like the EECA tool or can monitor the energy inputs and outputs. Normally I would work from first principals in which case the lower number would be the one to use. In this vain I was incorrect in saying that water heating has a COP of 1 if working from first principals, as that does not include cylinder losses.

 

Whatever, I still can't see a the system paying for itself. Perhaps Geoff Read can provide verifiable data that says otherwise?


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  Reply # 2117274 31-Oct-2018 10:12
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Another problem, the FAQ section of their website says that it heats water to 55deg. But hot water must be stored at a min of 60deg to prevent legionella from growing in the cylinder. Yet these higher temps required, lower the efficiency of any heatpump hot water system.

And for commercial it it even worse. As the Auckland council require that you have min 60deg water delivered to sinks in commercial kitchens. Which means that you need to set the cylinder thermostat to 70deg to reliably achieve that.

Can the Energie system achieve 60deg stored water temperature? As there are other heatpump systems that use a booster element to get from 55deg to 60deg.





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Master Geek
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  Reply # 2117292 31-Oct-2018 10:48
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From my understanding they have an anti-legionella function with timer-programming, to boost the temperature to 60deg using a standard electric heater element every now and then.


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Wannabe Geek


  Reply # 2117318 31-Oct-2018 11:20
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Absolutely correct, the Energie Eco system has an anti-legionella function where it heats the water to 60 degrees once a week.


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