Solar Flat Plate, Tubes or PV?

kerrypod

Hi, I'm wondering has anyone out there built a new house recently and used Solar PV panels to meet the Building Regulations? The PV panels seem to be much more expensive than the Solar Tubes at the moment, and I personally feel that the PV option offers a reduction in the electricity bill rather than just solely heating the water. My engineer has recommended 6sq.m of solar tubes plus a 300L cylinder to meet the Building Regs. If I had to settle for just hot water, I'd go with the Solar Collectors as they look more flush with the roof slates when installed.

So should I go Solar PV? Solar Tubes? Solar Collection? Is it worth the extra money for the PV panels? Or should I just stick with the cheaper hot water option? Note I am not using HRV or Air to Water heating.
Thanks

Calahonda52

Solar PV has a lot less complexity than Solar Thermal so just comparing panel prices is not meaningful.

The one think to remember about PV is that as long as the panel is exposed to light it is always generating elec: there is no off switch at the panel output level

You are much more highly to use all the power from the PV than the all the hot water.

Solar Tubes are more effective than flat panel

PS QQ below puts it a lot more succinctly.

quentingargan

The big problem with PV right now is that you don't get paid for surplus power that you export and you are unlikely to use more than about 30% to 50% of the electricity you produce.

You can get a unit like this to give you hot water from your solar PV if you aren't using the electricity yourself. On principle, I don't really like this because you are taking an energy with a higher value and downgrading it to just heat. It takes 2.37kw of oil to produce 1kw of electricity. Seems a shame to use electricity then to produce heat when oil can do that at 90%+ efficiency.

Solar thermal has more bits to go wrong - generally solar PV is a "fit and forget" installation whereas thermal needs glycol changed regularly and has pumps and expansion vessels which may fail over time, though good installation (and including a heat dump) can mitigate this.

I think the savings on solar thermal are over-rated. During summer, hot water can be obtained quite cheaply using night-rate electricity. I think in the long term, when a feed in tariff for surplus electricity is introduced (and it would be daft for this not to happen) then PV would be the obvious option. In the meantime, solar thermal or solar PV with a diversion device might stack if you use a lot of hot water.

kerrypod

Cheers for the advice, there are very divided opinions on this at the moment but i think the solar thermal may be best for now!

GLENNFALLON

So can PV be used in anyway to heat a home

quentingargan

GLENNFALLON wrote: »

So can PV be used in anyway to heat a home

I don't believe that solar can ever be usefully or economically used to heat a home. It works best when you need it least. You cannot escape the fact that solar energy is about 1.10th of the level in December that is is in June. You don't (or shouldn't) need to heat a house in June.

Solar, both PV or solar thermal may make sense because they can provide hot water during the summer when the heating system is off. Usually your central heating is less efficient in heating water at that time of year, so there is synergy.

Bass Cadet

GLENNFALLON wrote: »

So can PV be used in anyway to heat a home

Yes...There are solar PV panel systems that connect straight to your hot water tank. the system overall would offset your current electricity bill (depending on the size and a few other important factors...south facing roof etc.

There is a white paper expected in mid September which will hopefully have feed-in tariffs available for retrofit residential homes as they have in the North. Solar thermal is becoming a thing of the past...ie solar PV is becoming the industry standard for hot water heating and offsetting electricity bills.

cros13

quentingargan wrote: »

I don't believe that solar can ever be usefully or economically used to heat a home. It works best when you need it least.

Yes it can. Heat Pump. Air source or ground.

And proper modern Li ion home battery storage at $350/kWh to increase self-consumption.

A considerable amount of homes in Germany are already heated using those three technologies.

quentingargan

cros13 wrote: »

Yes it can. Heat Pump. Air source or ground.

And proper modern Li ion home battery storage at $350/kWh to increase self-consumption.

A considerable amount of homes in Germany are already heated using those three technologies.

You can't get away from the fact that in Dublin you get a tenth of the solar insolation in December that you get in July. So anything solar that supplies enough power for a heat pump (or any other heating device) in December will be producing ten times that amount of electricity in July.

Don't get me wrong - I'm a fan of solar, but I just think it has no place in home heating.

By the way, cycling lithium batteries is a lot more expensive than cycling lead acid. They're great for cars and mobile devices where you want to get the weight down, but they havnen't come close to cost per KwHr of cylcing lead acid batteries.

Solar PV is cost effective at producing electricity - particularly for commercial sites using power during the day. The only problem in Ireland is the total lack of any payment for surplus power exported.

murphaph

PV can make a lot more sense for those working shifts. You can park your electric car in the drive and charge it in the afternoon.