ASHP – Should do better - Must Do Better

KG-THPP

Apologies if this has been mentioned, but what do you think about the hybrid systems that glowworm have released?

semo

KG-THPP wrote: »

Apologies if this has been mentioned, but what do you think about the hybrid systems that glowworm have released?

This just seems like a bivalent system to me. You use a boiler when the heat pump can't keep up or when you want water hotter than 50°C.

KG-THPP

It comes with a box that decides if its cheaper to run your heating via the heat pump or by gas, then switches accordingly.

semo

KG-THPP wrote: »

It comes with a box that decides if its cheaper to run your heating via the heat pump or by gas, then switches accordingly.

What's the point of a heat pump if a situation exists when it is cheaper to run an immersion heater for example? The problem is that R410a systems have a reduced capacity at very cold temperatures (not necessarily reduced efficiency though). Add to that the fact that most heat pumps in the UK are handicapped (R410a was designed for air to air systems and air to water is not as efficient).

I would say don't believe them more than you would believe the marketing on ecodan and altherma systems. They all have/support backups in case they can't cope. Ecocute systems on the other hand have the potential to be much better. As I said, I will give the tech a go if my finances permit. I am cautiously optimistic as I doubt that every major HVAC company, several million Japanese consumers and the Japanese government are all wrong about R744.

richardc1983

semo wrote: »

What's the point of a heat pump if a situation exists when it is cheaper to run an immersion heater for example? The problem is that R410a systems have a reduced capacity at very cold temperatures (not necessarily reduced efficiency though).

The point is that for the majority of the year it is cheaper to run a heat pump than immersion/gas systems. Only at very cold periods do heat pumps struggle and as you have stated you have reduced capacity... reduced capacity = reduced efficiency as the heat pump is not outputting what it was designed to do but will still draw the same power input. Eg 1kw input and 3kw output but at -5C your output may be 2.7kw but you are still drawing 1kw... So whilst this may still be enough output to meet the heating needs of the house you have lost some efficiency but you have to decide when comes the point that it is costing more to run the heat pump. This is why they have backup systems to give a boost to what the heat pump is already making.

meric

semo wrote: »

I think you missed the point of my post. I have not read of a single topic discussing an ecocute system in a UK domestic environment. The technology is expensive because it is so new here in the UK. R410a refrigerants just don't cope all that well with low temperatures for water heating. I think the EST should make a new study and this time include R744 systems. Sanyo also make a 9kW system. Costs are still high but it would be interesting to know how these newer systems cope in the UK, compared to the current Ecodan, etc. installations

Semo, I know of a project carried out by some Strathclyde University students which included some monitoring of ecocute installations in houses in Scotland: as a new user I'm not allowed to post links, but if you google "ESRU ecocute", the website the students produced should be the first hit. Hope it's of interest...

Cardew

meric wrote: »

Semo, I know of a project carried out by some Strathclyde University students which included some monitoring of ecocute installations in houses in Scotland: as a new user I'm not allowed to post links, but if you google "ESRU ecocute", the website the students produced should be the first hit. Hope it's of interest...

Welcome to the forum, and thanks for an excellent link.

http://www.esru.strath.ac.uk/EandE/Web_sites/10-11/ASHP_CO2/modelling_EESmodel.html

The conclusions make interesting readings!!!!

<H5>Main conclusions for our project

From the results of our project, we are able to draw the following conclusions for this project:

• The performances of a CO2 heat pump in operation are influenced by the outside temperature and the energy used for the defrost cycles, as every conventional heat pumps. However, the main specificity of the CO2 thermodynamic cycles is that the performances will be very sensitive to the return water temperature to the heat pump which should be as low as possible.
• The coefficient of performance of a CO2 heat pump in operation is mainly determined by the outside temperature and the return water temperature to the heat pump. This was verified for the Sanyo CO2 heat pump whose COP has been expressed in function of these two parameters.
• Considering a particular heat pump, the frequency and the energy required for the defrost cycles are mainly influenced by the outside temperature and relative humidity. It is however a quite complex problem of heat transfer, psychometry and ice formation. Modelling accurately the defrost cycles is not straightforward.
• The performances of the CO2 Sanyo heat pump given in the technical manual from the manufacturer are confirmed. However some improvement will be required so that the potential of the CO2 technology are actually fully used. In particular, a better design could enable to decrease more efficiently the return temperature to the heat pump.
• In the case of the Sanyo Eco Cute system, the water return temperature to the heat pump is mainly determined by the water returning temperature of the heating system and the occurrences of the sterilisation cycles. The domestic hot water demand doesn't seem to influence the water return temperature to the heat pump since the cold water inlet from the city is located in the middle of the tank.
• The use of underfloor heating helps the CO2 heat pump run efficiently since it operates at lower temperature in general than the other heating system. Even if the Sanyo system enables to produce water at quite high temperature, the use of the system with radiators will induce a decrease of the performances since the return temperatures from the radiators tend to be quite high. Otherwise, the temperature drop in the radiators must be maximized as much as possible.
• The system runs a sterilisation cycle after every 4th compressor start where it takes the water flowing from the heat pump to the tank up to around 64oC. This is to try and inhibit the growth of Legionella bacteria in the hot water system. It would be our conclusion though that this sterilisation cycle happening after every 4th compressor start is excessive and decrease significantly the performances.
• The position of the sensors and the design of the tank are not optimised to limit the starts and stops of the heat pump and to meet an important domestic hot water demand without using the electric back-up heater. The tank is mainly used as a buffer storage for the domestic hot water but not for space heating.
• With an average COP estimated at 2 for the installations in Athelstaneford and Oban during the weeks of monitoring, the expectation for the seasonal performance factor (average annual COP) are not extraordinary high. If there is a potential concerning the use of the CO2 heat pump, the design of the tank will have to be improved to optimise the performances.
• The use of the other tank for the installation in Ballencrief doesn't bring any significant improvement in comparison with the Sanyo tank unit.
• A better understanding of the properties of the heat pump resulting in improved sizing and installation will allow the heat pump to operate as efficiently as possible for each individual dwelling.
• Studies have been carried out, looking at the design of the heat pump and hot water tank relationships. In particular a paper by Jorn Stene talks about the use of a "tripartite" system to maximise the efficiency of the heating system, more information on this paper can be found here

</H5>

lardconcepts

We might be looking at this again. We've been reliably told by the EST that there is an £850 ASHP "incentive" payment for now, and possibly RHI payments after Oct 2012, but no-one could be sure, and one though ASHP wouldn't be attracting any RHI at all, only GSHP. Which is odd, as they seem to have reached parity of efficiency.


The two quotes we got were:

• 1 x Danfoss DHP-AQ 11 kW heat pump
• 1 x Danfoss DHP-AQ Maxi control unit (inc. integral 180 litre dhw cylinder)
• 1 x 200 litre heating buffer store
• Anti-freeze solution
• Connection to the existing heating system supplied by others
• All electrical connections and certification
• Commissioning the system
• Installation registration on the MCS database

£10,306.47 inc vat - over the budget.

and

• 1 x Nibe 2015 11 KW heat pump
• 1 x Nibe VVM300 control unit (inc. integral 155 litre dhw cylinder
• 1 x Nibe UKV 200 litre buffer tank
• Anti-freeze solution
• Connection to the existing heating system supplied by others
• All electrical connections and certification
• Commissioning the system
• Installation registration on the MCS
database

£7,741.36 - after taking the £850 premium payment off, that's £6891. With the £3000k interest free loan for 5 years from the local council, that's just do-able without us having to borrow.

I wonder why the big pricy disparity, and I wonder why the raw materials etc are SO much more from an MCS qualified installer? There appear to be several people on ebay who'd do it for half the price. In which case, why don't I just go for them?

Now the next thing I have to try and figure out is how much a boiler costs to run per hour. The water heating part of our house is easy:

From http://www.lpg-solutions.co.uk/facts.html

4.16 litres= 1 therm = 100,000 BTU
0.141 litres = 1KW
29.3701 KW = 1 therm = 100,000 BTU
0.242 therms = 1 litre
7.08 KW = 1 litre = 24.170 BTU
1 KW = 3412 BTU
1 litre = 9.66 cu.ft
0.104 litre = 40 cu.ft
1 therm = 40 cu.ft
1 Kg = 1.985 litres = 47.132 BTU
0.512 Kg = 1 litre
2000 litres = 1000 Kg = 1 tonne = 474 therms
1 tonne = 18.880 cu.ft
3.85 litres = 1m3 Vapour

Details of our current boiler:
From: http://www.londonheatingservices.co.uk/boiler/Ideal-Classic-FF260P-NonCondensing-LPG-Conventional-Regular-Boiler.asp

FF260P Heat output in BTUs per hour: 56,997
Maximum power in kilo Watts: 16.7
Efficiency band: D
Efficiency: 78.5%

Assuming we pay £52.50 per 47kg of LPG, how much, per hour, would the boiler cost to run assuming it ran for 75% of the hour at 80% efficiency?

lardconcepts wrote: »

One idea I had was to built a small cheap conservatory to house the ASHP outside unit, to reduce the effects of the low winter temperatures with a bit of daytime passive solar gain. Madness or not?

I asked the company doing the quote about this - he said it wouldn't work as it would create it's own super-cold "micro-climate" in the conservatory, which could be colder than outside. He has a point - but what about thermal mass of the floor? There MUST be a smarter way than having a heater heat and element for the defrost cycle?

richardc1983

lardconcepts wrote: »

I asked the company doing the quote about this - he said it wouldn't work as it would create it's own super-cold "micro-climate" in the conservatory, which could be colder than outside. He has a point - but what about thermal mass of the floor? There MUST be a smarter way than having a heater heat and element for the defrost cycle?

Absolutly bonkers the company is correct installing it in a conservatory of any kind will turn it into a giant fridge freezer.

Have a look at this picture for example of what happens when installed in an enclosed space... the outdoor units need fresh air and plenty of it as it will just draw heat out of the space and get colder and colder and colder in there. The harder the unit has to work to remove heat from the very cold air is more inefficienct than the defrost cycles itself. Defrost cycles will be more regular with the below consequences if not installed in the right place.

Source: http://www.refrigeration-engineer.com/forums/showthread.php?32077-Unusual-split-install-in-Devon & http://www.refrigeration-engineer.com/forums/showthread.php?4229-How-to-make-ice-with-a-heat-pump

1. This was installed outside but in too an enclosed area:



2. Installed indoors:

rogerbanana

hello lardconcepts,

this quote you have seems a bit over the top.

the one i have for a fourbed detached,cavity wall ins. using a 12.5 kw unit is under £5000, fully installed.

i have had to greatly increase the rad. sizes as the surface area was insufficient , thats the only mod. they say i need for a good system.

check out " husky heat pumps" on the internet , they install all over the country.