Choice Choices - HP + PV or Gas + Solar or Oil + Solar

fclauson

Ok

I have posted a lot to this forum - I know need you help in making a decision

Making a choice about the best heating system for a very well insulated house which needs to meet Part L

Each of the options posted can meet Part L - and the demands of the house but they do it by taking varying approchs approches

Each has it benefits
HP + PV - all electrica, no local polution, but wholly dependant on electricy
Solar Thermal + Gas - clean - simple, all kit lives in the house, but you have to have tank in the garden
Solar Thermal + Oil - similar, lots of engineers out there who understand it, not very innovative
Another - you choose

Do-more

Solar Thermal + Oil

Need a bit more info FC.

What's your primary motivation? Capital cost? Running cost? Sustainability? Security of supply? Concerns about possible CO2 or NOX taxes?

We also probably need some figures on what you expect your heating and DHW demands to be. This is particularly important when considering a heat pump.

When you get down to low demands the energy consumption of the circulation pumps start to have a huge influence on the overall COP of ground source heat pumps. For a passive house there is little difference in COP between air source and ground source but the air source normally wins hands down on capital cost.

Air source will also win against ground source if you are using a heat pump to produce DHW in the summer time i.e. Not installing solar thermal as well. Also the balance between space heating and DHW will influence what type of air source to go for. If DHW is 50% or more of your total demand then it's probably better to go for a CO2 ASHP

I've only done rough figures on solar PV (because I don't have the money anyway) but on them the economics don't stack up yet (and I can get a grant for 35% of the capital cost) but I firmly hope that improvements in technology may well tip the balance within 5 years.

fclauson

Do-more wrote: »

Need a bit more info FC.

What's your primary motivation? Capital cost? Running cost? Sustainability? Security of supply? Concerns about possible CO2 or NOX taxes?

Yes - optimise all of the above

Do-more wrote: »

We also probably need some figures on what you expect your heating and DHW demands to be. This is particularly important when considering a heat pump.

Assume 50% for each

Do-more wrote: »

When you get down to low demands the energy consumption of the circulation pumps start to have a huge influence on the overall COP of ground source heat pumps. For a passive house there is little difference in COP between air source and ground source but the air source normally wins hands down on capital cost.

Getting to these "true" running costs seems to be very hard - no one is prepared to share

Do-more wrote: »

Air source will also win against ground source if you are using a heat pump to produce DHW in the summer time i.e. Not installing solar thermal as well. Also the balance between space heating and DHW will influence what type of air source to go for. If DHW is 50% or more of your total demand then it's probably better to go for a CO2 ASHP

I've only done rough figures on solar PV (because I don't have the money anyway) but on them the economics don't stack up yet (and I can get a grant for 35% of the capital cost) but I firmly hope that improvements in technology may well tip the balance within 5 years.

I can get a 2300 Kwh/annum for about €5500+vat installed

Do-more

Solar Thermal + Oil

fclauson wrote: »

Yes - optimise all of the above

Not asking for much!

Whilst I keep an eye on all the above factors myself, I don't weight them all with the same importance and was hoping you would prioritise them as it makes offering you a solution so much easier.

So for example if your priorities mainly lie with the middle two on the list and you don't mind putting in a bit of work then I'd suggest a wood pellet boiler and a pellet mill so you can make your own pellets from grass, leaves or straw.

But if you are most concerned about the first two I'd say go with the gas boiler and ask about sinking the tank underground or grow some bushes around it if you're worried about aesthetics. You'll hardly need a big tank.

Somebody might even get their finger out and start digesting household waste and seaweed as they do here to produce biogas and that would take care of most of the rest of the list.

fclauson wrote: »

Getting to these "true" running costs seems to be very hard - no one is prepared to share

There are always some assumptions to be made but calculating the entire electrical consumption of a heat pump and associated pumps or fans shouldn't be a problem. The biggest difficulty is more likely to lie with badly sized or poorly installed systems.

I'm going for an air source heat pump and solar panels myself but that is primarily because it's the best of a limited range of solutions open to me here in Sweden, you have a wider range of practical options available to you and I think gas is your best option.

It's part of the new building regs here that you must log your building energy usage broken down for heating, DHW and general consumption for a 12 month period within the first 24 months of occupation so I imagine that within a few years there will be plenty of data for the academics to analysis and try to interpret.

fclauson wrote: »

I can get a 2300 Kwh/annum for about €5500+vat installed

So what does that boil down to? I'm guessing it will reduce your yearly electricity bill by about €435? So something like a 14 year payback not accounting for inflation or interest payments if the money is borrowed or maintenance costs, my understanding is the inverter will require refurbishment or replacement possibly a number of times in that timespan.

Even counting on huge price inflation, it doesn't appear to make financial sense to me if those figures are correct.

No6

Build a passive house and leave out the oil, gas and gshp!! You should consider solar thermal for DHW then.

abyss

Solar Thermal + Gas (want to have boiler in side)

No6 wrote: »

Build a passive house and leave out the oil, gas and gshp!! You should consider solar thermal for DHW then.

Exactly.
One from my friends in Poland has passive type big house (presume 300 square meters/3300 sq foot/ + garage) and he don't need to use additional heat - even in winter time, when typically is minus 10 Celsius. House was designed and built as "passive" with excellent insulation, heat recovery ventilation, additional heat pump and other things. His brother was manager of something like energy efficiency agency and help prepare this project for him.

ccsolar

No6 wrote: »

Build a passive house and leave out the oil, gas and gshp!! You should consider solar thermal for DHW then.

+1, No 6 has it bang on the mark

fclauson

Thanks for your responses - but

1 - a Passive house will need a continous source of heat for somthing like 250 days of the year here in Ireland - mine will need a continous 3.5Kw at 0 degress - day and night to offset the heat loss. So you need some form of back up heating

2 - this is Ireland not Poland (or Germany or any other part of main land europe) - two differences
a) insolaiton - check out http://en.wikipedia.org/wiki/File:SolarGIS-Solar-map-Europe-en.png - Ireland receives a lot less solar gain than much of europe (but you knew that ) - so you cannot rely on solar gain to keep the house warm
b) moisture - ireland has a very high average moisture level - see http://www.sage.wisc.edu/atlas/maps/avgannrh/atl_avgannrh_eur.jpg (again you knew that too )

So with the above - you will need a source of heat to keep the house warm and dry. Solar will not provide much in the winter (say about 20% of the summer levels)

Given this - then which is a better investment
Solar + Oil or gas or timber stove or ......
HP

If you look at the numerics what does it take to install say 6sqm of solar plus a large thermal store and some form of back up heat source vs a HP

Then look at when you will have a demand from you heat source (winter time) and what it will cost to meet that demand

Take a look at the attached - it assumes no cost to money - but takes into account inflation etc.

This is for my house - which meets the 15Kwh/M2 passive standard

BryanF

fclauson wrote: »

Take a look at the attached - it assumes no cost to money - but takes into account inflation etc.

This is for my house - which meets the 15Kwh/M2 passive standard

as were in the renewable energies section, just to add the heating fuel options are not associated with CO2 reduction, which is what the passivhaus should maybe be pushing a bit more (past its obvious approach in reduction in m2/kwh's which is great) though maybe the title should read 'cost' choice of fuels..

sas

Solar Thermal + Oil

I'm already committed on solar and thermal store so this was a question of Oil versus LPG for me.

I was concerned about the lenght of contracts for LPG but as it turns out the main supplier is only a 2 year contract.

They also said that it's only a matter of time before the competition authority gets rid of contracts altogther so that's no longer a concern.

I'm going to look into LPG in more detail now.

meehano

Hi,
I'm in exactly the same position as you SAS, I was at the self build exhibition at the weekend in Belfast and came across the ROTEX Gas Solar unit. Only problem is, there is no-one around the north west with one installed to have a look at and ask all the relative questions!! The guy at the stall maintains that there is a 45% saving to be made against regular oil with this unit????

fclauson

meehano wrote: »

Hi,
....The guy at the stall maintains that there is a 45% saving to be made against regular oil with this unit????

45% of what !!!

I would ask that you get the data - do the maths so you can make an informed decision.

Look at
a) your annual h/w deamnd = V1 Kwh/annum
b) your heating demand = V2 Kwh/annum
c) what solar could give you = V3 Kwh/annum

V1 + V2 - V3 = demand from secondary heat source V4

V4 * Kwh rate for the energy source you have chosen
= running heating cost per annum V5

then look at different systems with the maths
Oiginal system costs + (V5 + Annual maint costs) * 15 years (allowing for inflation increase @ 8%)

Gives a 15 year life time cost which is probably when it will need mending or replacing

look at the following systems configs
gas + solar
oil + solar
biomass
HP

You might be very supprised which one wins - please post you answers

(the above assumes no losses and totally optimised use of everything - so its a bit rough and ready but its guide)

keru

I am tying to decide on the same issues. We are building an ultra low energy demand house. Let's assume it is of passive standard. 210 m2 house for a family of 5. I don't have any figures like you guys but common sense speaking here.

I assume passive solar gains to be small if not negligible due to our lovely climate. This dictates some form of heating for winter months albeit small compared to traditional house demands. I am hoping to meet that demand by having a solid wood stove, room sealed ( more pricey from €1500) and assume the HRV will propagate the heat around the rest of house. I have no problem plugging in a small electric heater once in a while when too lazy, sorry, read busy, to light the stove. Space heating sorted.

The problem is DHW. How do we get cheap hot water, all year round?
Solar panels are only good in summer and need back up in winter. This could be provided by adding back boiler to the stove. This solution sounds great but a few problems come to mind:
1. The stove capital cost goes through the roof (€3500 to €6000) as it has to be one of the very few room sealed boiler stoves needed for airtight houses.
2. I am told I will need a huge buffer tank of approx. 800l costing around €2500
3. Evacuated tube panels estimated at approx. €2500 for 8 or 9 m2
4. What happens when the stove is not lit in mid season because it is mild but grey? It would be wastefull to light the stove for hot water and open the windows because the house is overheating? I am assuming the immersion will be used then and for the few instances of winter days when stove is not lit through laziness.

The million dollar question is how much will it cost to use the immersion on a 800litre tank on those occasions? According to Electric Ireland it costs €21.87 per bill to heat a 210l tank from cold once a week. Lets assume I have a €150 cost per year for running the immersion. I think it would probably be more but for argument's sake... that should do!

So far I have capital costs of boiler stove, tank, panels minimum= €8500 and running costs of €150.

I know none of you like them but what if we enter thermodynamic panels in the equation? I get all my DHW all year round from them.
I was given a costing for tank plus panel commissioned for €5400
Now I can get a simple stove at €1500
Total capital costs €6900
Running costs were given at €200 per year. Lets assume it is more and use a figure of €300

Solution 1 boiler stove + solar thermal:
capital costs 8500
running costs 150
over 10 years 1500
total 10000

Solution 2 stove plus TDSP
capital costs 6900
running costs 300
over 10 years 3000
total 9900

Solution 1
Pros proven technology, should not break down or need replacement
Cons DHW and heating are linked, can't get one without producing the other in winter
High labour ( stove)could be problem when we get older
Risk of space overheating.
higher initial capital costs
lower running costs

Solution 2
Pros independent space and DHW systems. No risk of space overheating
Lower labour if stove not used as much as when working for DHW
Lower initial investment
Cons Higher running costs
Risk of compressor trouble, need for replacement over time?

It is hard to call really. I think I prefer solution 2 better for the independence of space and DHW production and no risk of overheating. I also think that in time PV panels could be something to add on to lower the running costs.
Come on, tear my theory apart?!

keru

Forgot to mention that wood supply for stove is free in my theory.

Do-more

Solar Thermal + Oil

@keru

If you do a search here you will find a number of recent threads with people complaining that their HRV system is not moving heat from warm areas to cooler areas around the house as they thought it would.

Air has a very low heat capacity, so to distribute any significant amount of heat you have to run the fans very fast to move enough air.

But the more air you are moving the higher your ventilation losses will be as the system efficiency is below 100%. And you will have problems with noise.

That aside you then have the problem of how you will heat your bathrooms which all have extract vents.

I've been around this circle already. At the very least you will need to heat all your extract rooms, kitchen, utility, bathrooms to fairly high temperatures 25C+ all the time to maintain 20C in the other rooms and that generally means putting in some sort of wet heating system, so if that is the case it is as well to have that heating system throughout most of the house.

I'm building a dormer bungalow and will have wet UFH on the ground floor and a water to air heat exchanger in the branch of the HRV duct to the bedrooms to keep them at about 17C. I'm undecided if I will have wet UFH in the upstairs bathroom or just use electric UFH.

I'll use an air to water heat pump for both heating and DHW year round. The heat pump and UFH system will end up at around €16K fitted. And should give me a running cost of around €400 a year.

You could lower the installation costs a bit by going for a gas boiler and thermal store (it's not an option for me) but I really don't think you will manage to do your heating the way you propose.

fclauson

I agree with Do More - you will need some for of heat as he describes. Remember that a passive house requires a CONTINUOUS SOURCE OF HEAT all be it very small - but if the structure starts to cool (say you are away for a few days when that Irish dark and damp foggy weather is about) then it will take a lot of energy to lift the building back to 20 degrees

Also with your pricing - check very carefully - having been a very big advocate of SP and thermal store - there are a lot of valves and pumps which need to go with this and these can bump up the price a lot. Same with mixing in you back boiler - its not as simple as some would have you believe. You have SPs at 2500 - I think thats a lot less than it will cost to install

I despite much reservation about 3 months ago am going for a pure GSHP for all my needs - (I am some turn coat I can tell you) - can supply heat at 3KwH all the time which is required at 0 degrees

Couple of other points - yes there is solar gain in the winter - get (or do your self) a PHPP calc (you learn so much doing it yourself)

On the 800L - make sure it has a baffle at about 300L so you effectively have two tanks in one - and only need to heat the top part for hot water

I think its a very close call as to the system one uses - my heat demand is below my h/w demand across the year - so I should be optimising for that - but then from oct -> march I will need a long slow small amount of UFH heat - so you have a real conflict as to the perfect solution

Hence my rather crude maths to work out which is best and have used a 15 year window to see how this works

By the way - jealous of you "free" wood - don’t read the thread about burning wood can be more polluting than oil - you will just get upset

keru

fclauson wrote: »

I agree with Do More - you will need some for of heat as he describes. Remember that a passive house requires a CONTINUOUS SOURCE OF HEAT all be it very small - but if the structure starts to cool (say you are away for a few days when that Irish dark and damp foggy weather is about) then it will take a lot of energy to lift the building back to 20 degrees

Also with your pricing - check very carefully - having been a very big advocate of SP and thermal store - there are a lot of valves and pumps which need to go with this and these can bump up the price a lot. Same with mixing in you back boiler - its not as simple as some would have you believe. You have SPs at 2500 - I think thats a lot less than it will cost to install

I despite much reservation about 3 months ago am going for a pure GSHP for all my needs - (I am some turn coat I can tell you) - can supply heat at 3KwH all the time which is required at 0 degrees

Couple of other points - yes there is solar gain in the winter - get (or do your self) a PHPP calc (you learn so much doing it yourself)

On the 800L - make sure it has a baffle at about 300L so you effectively have two tanks in one - and only need to heat the top part for hot water

I think its a very close call as to the system one uses - my heat demand is below my h/w demand across the year - so I should be optimising for that - but then from oct -> march I will need a long slow small amount of UFH heat - so you have a real conflict as to the perfect solution

Hence my rather crude maths to work out which is best and have used a 15 year window to see how this works

By the way - jealous of you "free" wood - don’t read the thread about burning wood can be more polluting than oil - you will just get upset

Thanks for your Comments. If I have to invest near 15k in heat installation then what's the point of the passive house?

fclauson

keru wrote: »

Thanks for your Comments. If I have to invest near 15k in heat installation then what's the point of the passive house?

Good point - there are passive designs which need very little heat - but at a price (see an active thread on main forum)

So its back to my mantra of

• Passive
• Practical
• Pragmatic
• Price sensative

Do-more

Solar Thermal + Oil

keru wrote: »

Thanks for your Comments. If I have to invest near 15k in heat installation then what's the point of the passive house?

Well that is the $64,000 question and one that only you can answer for your circumstances.

For me it's a question of using passive house principals to achieve the lowest future running costs at a reasonable capital cost.

In my case, I'll end up with a house that will have running costs of about one third of the cost of a house built to the building regs. and that for me is a huge comfort.

I won't have a passive house, it will be on paper around 22kW/m2/a but my build cost is significantly less than if I were to certify the house.

I hope that if the cost of PV solar continues to drop, within 5 years I will only have to spend about €15,000 or less to completely offset my running costs.

fclauson

Do-more wrote: »

Well that is the $64,000 question ....

Note quite - but it could be €10K question

Do-more

Solar Thermal + Oil

Thinking about this further keru there are some points to add which may help in answering your question, "what's the point of passive house?"

Passive House is a particular philosophy for house building which is primarily focused on providing high comfort levels for the occupants of the house.

So with a passive house you should have a very stable indoor environment with good ventilation and very little fluctuation in temperature. (The normal target is 20C year round.)

Hand in hand with that, it looks to minimise the amount of energy required to achieve those comfort levels.

So it's not about "how can I design a house without a heating system?" it's more "how can I have a very comfortable house to live in with minimal running costs?"

So in following the passive house design philosophy the house will be built with high levels of insulation and airtightness and have energy efficient heating ( & cooling if necessary) and ventilation systems, making use of any passive gains available in order to achieve the primary goal of a very comfortable living environment.

In some climates it is possible to achieve that without a traditional heating system but unfortunately the Irish climate is not one of them.

keru

I am on the same course than you all; not passive certified but cherry picking the elements that will bring us to low running costs and comfort at best investment value. The vast array of options can sometimes be overwhelming especially when combined with forcefull salespeople and general lack of knowledge and pragmatism...

solarstudent

Have you considered Heat Pump and Solar thermal? no oil or gas?

fclauson

yes I did but the economics is just not there

ST cost around €4K to €5K to install to save say €200 per annum - payback is then for ever

solarstudent

fclauson wrote: »

yes I did but the economics is just not there

ST cost around €4K to €5K to install to save say €200 per annum - payback is then for ever

What is your annual heat and electricity bills combined? they would want to be very small for you to say that the economics are not there?

fclauson

see my graph at in another post comparing HP vs Solar + Oil

all the maths is there

ECO_Mental

hi lads,

I think I have come to a decision after about two years thinking about it

Firstly my Situation;
House approx 250 msqr
Construction Closed Panel Timber Frame
Airtightness less than 2 ac/hr
Yearly Energy Requirment assuming b1 hoping to achieve A3 so say around 75kWh/m2/yr, so total 18750 kWh
Location Cork Rural no natural Gas, South facing should have good solar gain.

Anyway the choices are

Pure Elec Heating & Solar Thermal
LPG & ST
Oil + ST
GSHP
Air to Water

I decided crunch the numbers, its the only way really and I was surprised at the results but feel free to correct my assumptions and the way I have done the calcs.

The way I see it no matter what system you go for the capital costs for your heating and DHW are going to be around the same, around the 15k mark if you excluded MHRV which every body has to have if you have an airtight house. With LPG you have the added expense of a tank, the same with oil and then you have get ST to meet Part L so it all adds up.

Cutting to the chase so, I think the best way forward is just Air to Water for all DHW and Heating, no solar thermal.

Because when you discount the capital costs its all about the cent per kWh and with a COP of around 4 that brings down the elec price to around 4c kWh. I have discounted GSHP purely because of the the extra €3-5k capital of the bore hole. Might be better constant COP in very cold weather but in reality that might be one or two weeks a year.


Reasons For Choosing Air to Water
Cent per kWh
One system, no problems trying to integrate with other energy sources.
I will only have one utility bill, easier to manage hopefully night time usage etc, albeit a bit bigger
And again cent per kWh

Now I know there are problems with heat pumps and I was leading the charge against them up until two weeks ago, but I think this is the simplest solution to the problem.

That has been my whole design mantra keep it simple, and trying to manage 2 or 3 energy sources is not simple and I feel that you will not get the benefit.

I have attached my excel sheet for comments. Some assumptions used
SEAI Energy Prices
I have given a handicap to some systems for responsiveness.
The Air to Water Prices are correct as of two days ago.
Others costs are best guest, but feel to change but I think they are roughly right.

Also if I missed some thing.

Regards
EM

Oh Forgot, I do not hold responsibility for any viruses, malware etc in the excel doc. but I have antivirus software so it should be grand

fclauson

good analysis

in a rush so just some quick comments
1 - think about inflation (see the excel PV function for this)
2 - think about splitting the h/w and heating demand and using a COP of 0.75 * your COP for h/w (thats what DEAP does)
3 - think about GSHP - you can put the pipe work under your perculation area if you have one
4 - think about night time rate - I have found it hard to justify - you pay an extra 50 or 60 per year for it which is like paying at full value about 600Kw/annum for the first night time units you use


When you work out the 15 years costs with inflation think about moving some of that money into insulation and a better build fabric - i.e . spend now save later

ECO_Mental

fclauson wrote: »

good analysis

in a rush so just some quick comments
1 - think about inflation (see the excel PV function for this)
2 - think about splitting the h/w and heating demand and using a COP of 0.75 * your COP for h/w (thats what DEAP does)
3 - think about GSHP - you can put the pipe work under your perculation area if you have one
4 - think about night time rate - I have found it hard to justify - you pay an extra 50 or 60 per year for it which is like paying at full value about 600Kw/annum for the first night time units you use


When you work out the 15 years costs with inflation think about moving some of that money into insulation and a better build fabric - i.e . spend now save later

1. I didn't take into account inflation as I am assuming that it will be the same across all systems and will cancel each other out. eg oil goes up, LPG and Elec goes up.
2. Need to look at it, would it make much of a difference.
3. Never thought of that, good idea. I will have to put in a percolation area anyway so it makes sense. Also you would do away with the ugly outside fan unit.
4. Regarding night time rate, I just used the SEAI rates but putting 40% of your load on night time (possible?) will make things better for the Air to Water. About €100 a year with 40% I have said that the extra over for the night standing charge is €70 might be too much but its small change in the grand scheme of things

See attached excel sheet with compensation for night time

fclauson

You forgot to comment on moving running costs in to insulation

On the change for Hotwater COP - not much difference until you lower your heat demand by way of being better insulated and then you h/w becomes 30% of your overall demand. My heat demand will be around the 6000 Kwh for a house which is larger than yours. Hence my comment about moviing ruuning costs into upfront insulation.

My h/w will be around 2700.

Do-more

Solar Thermal + Oil

If it's any addition I have come to the same conclusion ECO Mental.

Mine came down to a straight decision between GSHP and ASHP and whether to add Solar thermal or not.

Likewise the added capital cost of (in my case) two boreholes firmly swung the balance in favour of the ASHP.

Because of the anticipated COP of producing summer time DHW with the ASHP the payback isn't there for the solar panels.

I remains to be seen if the estimated running costs are realised in reality but I am comfortable that I have made the right decision for my circumstances.

ECO_Mental

Do-more wrote: »

If it's any addition I have come to the same conclusion ECO Mental.



Because of the anticipated COP of producing summer time DHW with the ASHP the payback isn't there for the solar panels.

I think you are right €3-4k will buy you a lot of electricity if you dont add ST. Considering that ST is only useful during the summer months anyway.

Right I think that decision made:cool: Air to Water only.....for all Space and DHW heating

(although might look again at the capital costs of GSHP considering that I will be digging for a percolation area anyway:))