Solar Thermal

ispookie666

Just came across this
 https://sahp.info/sahp-retrofit
Is it possible to integrate this or similar into a normal fossil fuel wet hot water system?  

Netexporter

The details are a bit sparse but I'd imagine you'd need a hot water cylinder with two heat exchange coils, one for the fossil fuel system and one for the heat pump. Or disconnect the fossil fuel boiler from the hot water system and just use the existing coil with the heat pump.

I don't think you'd see your money back in any sensible time period, even using diverted solar.

ispookie666

The part of needing two coils is what was not clear. If they were marketing this as a retrofit, maybe they would have to specific which type of what pump. Not sure if it would be suitable for ASHP either 

Netexporter

Not sure if it would be suitable for ASHP either 

There wouldn't be much point, with an heat-pump. You could just program that to heat water when there was surplus /cheap leccy.

70sbudgie

I think this is interesting, though as previously mentioned, the website is a bit light on technical specs. To me it looks like they are heat pump cylinders that use an evaporator panel instead of a fan. With one model being just the heat pump (and evaporator panel) so it can be retrofitted to an existing cylinder. 

The solar connection appears to be similar to the more common solar diverters, but the unit makes it a heat pump version and therefore (hopefully) more efficient than a standard immersion heater. 

70sbudgie

Just reading the brochure (that I managed to download without giving them my phone number) and it has a lot more information.

"Solar Ready

With a growing number of consumers 

now generating their own electricity from 

Solar PV, our range of Solar Assisted Heat 

Pumps incorporate intelligent controllers 

that have the capacity to send & receive a 

digital signal from a PV inverter in order to 

be notified when an inverter may be 

generating or exporting electricity.

When the systems receive this notification 

they act as a battery, heating the water 

within the hot water cylinder to a higher 

temperature, thereby storing the 

generated electricity in the form of hot 

water, ready to be used by the consumer 

when they need it."

HP thermal power (Max.) 2,000W

HP electrical input (Avg.) 500W

Is this suggesting an average CoP of 4? Though it's not a massively helpful number without knowing how they've calculated the average.

zeupater

Hi

Search the forum for 'thermodynamic' and you'll find a number of discussions, probably around 10 years ago!

I've seen similar in operation overseas (actually home + dhw heating!) and unfortunately the performance was described at the time as 'highly disappointing'.

HTH - Z

70sbudgie

I hope the technology has improved over the last 10 years, not least because heat pumps seem to have improved (or is it just that they've become more popular?) Nevertheless, I will have a look for the discussions you suggest.

I've found some more information on solar assisted heat pumps (I'll add links at the bottom for those interested). When we replaced our boiler and got a hot water tank, I chose one with a dual coil for solar thermal. But I couldn't ever make the finances for solar thermal work out and ended up getting PV instead.

I am very interested in them, for a few reasons. The second coil in my DHW tank should mean that a retrofit HP could run in parallel with my existing boiler and /or the HP that I hope will eventually replace my gas boiler. I like that they can be mounted vertically on a wall - this means I have more space to install a panel as my roof is a bit full. I also like the concept of energy sources for heating and DHW being separate (even if they both use a heat pump). I haven't yet worked out whether this would be more efficient or not.

I am also intrigued by the idea of a passive evaporator panel instead of the fans we usually see for ASHP. The benefits are clearly lower noise "pollution", but does that compromise the efficacy?Ideally, I'd love to find a technical comparison between fan and panel HPs. 

But I am increasingly wondering whether I will eventually come to the same conclusion as I did for solar thermal, that the numbers just don't add up. There seems to be a similar reluctance to share technical performance data, which makes me suspicious.


https://heat-pumps.org.uk/solar-assisted-heat-pump/
https://energysavingtrust.org.uk/advice/solar-assisted-heat-pumps/

zeupater

Hi

Maybe there have been some improvements around the edges if someone's invested in decent compressor technology, but I'd really be surprised if they have done as the solution is simply a roll-bond evaporator plate with an immersed condenser coil .... if the solution is perceived to be any good the bigger players in the refrigeration/heat-pump industry would be putting their reputation behind product offerings .... so the question is, where are their units ??

Anyway, just looked up a previous post that linked to a technology comparison you may be interested in ... https://forums.moneysavingexpert.com/discussion/comment/73063474#Comment_73063474

... however the link included in the post looks to have been moved/deleted, don't you just love technology ....  ..... bit of a search around turns up what I believe is the same info .... https://www.decerna.co.uk/wp-content/uploads/2014/11/COP-of-water-heating-technologies.pdf

HTH - Z

70sbudgie

Thank you for that @zeupater It seems interesting that the two methods that use heat pump technology have relatively similar COPs. Which suggests there might not be a huge difference between the different collection methods and it is the compressor that does the most work.
Though the scientific method for the ASHP seemed a bit less rigorous. 

What is interesting is that the solar thermal was so much better. I wonder whether the improvements that (may have happened) since the test include combining the solar thermal panel technology with the HP / compressor technology.

Though it I believe the area for the thermodynamic plate was considerably smaller than the solar thermal (0.8m2 Vs ~4m2)

What it does mean is that I will be looking for more information on the evaporator panel tech (how much does it resemble a solar thermal panel).

zeupater

Hi

The thermodynamic plate is roll-bond, effectively a metal sheet into which channels are pressed before folding, bonding & painting, it's exactly the same as used as evaporators in many fridges & freezers ... as such it's not new technology and it's been the basis of thermodynamic panel solar offerings as long as I've been following the technology.

I first came across the passive thermodynamic panels at a work colleague's home in Sweden where he was extremely proud to show off the 'new' addition .... about a year later we met was at a conference in Brussels where he wasn't so pleased as it seems that the system was pretty 'useless' for anything other than making 'piles of snow' .... 

... yes, snow .... the cold panels cause condensation which forms frost which insulates the panel from the ambient temperatures and reflects any sunlight, which causes a defrost cycle, which reduces efficiency, the frost slides off into mounds of 'snow' and then everything repeats ... the difference between summer & winter is that efficiency increases proportionally to sunlight hours and the piles of snow melt at different rates .... sufficient to say that the system had been replaced before we next met ... 

It's not that his home is anywhere near the north of Sweden, it's somewhere on a line between Oslo & Stockholm, so somewhere equivalent to Scotland so I'd expect not too dissimilar seasonal performance in the UK ... if we were talking about much sunnier areas, such as around the Med or southern USA, the solution likely wouldn't have so many issues, but then again, in those areas standard solar thermal DHW systems are far more common and far more efficient ....

Disclaimer ... we have solar thermal (vacuum) and still (just about!) haven't used any form of alternative water heating since early Spring ... could do with a couple of consecutive days of continuous sunshine to keep MrsZ happy though, she tends to have a shower temperature threshold much higher than me and I did notice yesterday that although the the cylinder temperature was still pretty decent at the top, the middle was suffering a little .... 

HTH - Z