Mastodawn

We fitted solar thermal (hot water) panels when re-roofing in 2006. They've been great and very cost effective. Added solar PV around them in 2011. In 2023, using over 10 years import/export data I calculated the optimum extra PV/batteries needed to satisfy most of our power needs and covered a shed in PV. The shed is south facing with a 20 degree roof. The vertical panels help in winter.

The main fly in the ointment is the shadow from one of my mature Ash trees. I planted 800 Ash, among over 2500 trees in my "wildlife area", but they almost all died of There is no way I'm felling a mature tree of any kind, especially Ash! This does mean I get reduced winter generation for a few hours when it's sunny.

Although I am G100 limited to 6.5kW export, the whole of the battery/charge controller system sits on the DC side of the installation (invisible to the grid). So, when it's sunny, I have seen 16kW going into the batteries. Meaning the 28kWh batteries could potentially be charged from empty in under 2 hours.

... the next year (2024) we installed heat pumps. Air to water would have been very tricky in our house, so we went with Air to Air, which many people (v.annoyingly) call "AirCon". Ours are Mitsubishi Electric. Bought 99% for heating, but means we get free cooling, should we need it, in the summer. There is no mains gas here but, over the years, we've used oil, smokeless coal, logs and wood pellets. With Octopus Intelligent Go and batteries we almost never pay over 7ppu for electric.

I would be very interested in people's opinions on green water heating solutions. Our air to air heat pumps don't provide hot water. In the summer we mostly get it from the roof Solar Thermal, but on cloudy days and winter we would need to use the electric immersion heater or the oil boiler. Has anyone used a dedicated hot water heat pump, with exterior heat exchanger panels? Our plumbing system is also very complicated, so may not be easy to integrate.

Peter Brown 11h ago

@ArborealTechie it’s not easy to even start to answer without knowing how your existing system works. Do you have a hot water tank and if so, how large is it? Is it well insulated? If there is no insulation on your hot water tank or there is no hot water tank then you are probably better with on demand hot water. If you have a high demand for hot water, it might be well worth getting renewables involved.
But if you have an electric shower your demand for hot water is probably minimal.

@peterbrown Thanks Peter. All good points. Like everything here the answer is complicated! We have an electric shower but it hasn't been used in years. We have a 200l heat store tank, with immersion heater and multiple internal heating coils. Water can be heated by electric, oil, coal (Rayburn with back boiler) and solar thermal. We use a shower with close to mains pressure from the heat store. If I get a "green" DHW solution I may need to sacrifice some of the existing flexibility.

@peterbrown ... hence I really just want feedback from people who have experience of alternative water heating systems, to see if it's worth making major changes to my system. We also have a Dunsley Neutraliser for the Rayburn connection!

Druid 🏴󠁧󠁢󠁷󠁬󠁳󠁿11h ago

@ArborealTechie Do you have multiple indoor units? And if so, does each need it's own external unit or is there just one?

@druid This place is quite unusual, due to bits of it being different ages and of different construction. We have a single indoor unit in my office, with a dedicated outdoor unit, paid for by the business. Then there is a "multi-split" outdoor unit, serving three indoor units, two of which have up to 5kW output in large rooms. Then there is a multi-split serving three bedrooms, the kitchen and lounge. Most houses with air to air have a single outdoor unit (afasik).

Druid 🏴󠁧󠁢󠁷󠁬󠁳󠁿10h ago

@ArborealTechie Ah, I see. Does sound complicated. I wonder if it would be possible to upgrade your external units to just one more powerful one instead? Perhaps that could give an energy saving? Just a thought as I have no knowledge of these.

@druid That would be reasonable, except for the topography and the way the different parts of the house are used. This way is more efficient, as we almost never have all three outdoor units in use at the same time. Like I say, it's complicated!😉

Druid 🏴󠁧󠁢󠁷󠁬󠁳󠁿10h ago

@ArborealTechie Just going back to air->water, as you're already with Octopus, I'm sure you will have seen this before. Their 'Cosy' heatpump sounds good.

https://octopus.energy/cosy-heat-pump/

Cosy heating | More than just a heat pump

Introducing Cosy heating - more than just a heat pump

Octopus Energy

@druid Yes, they do sound good. From what I've heard they do good installations as well. I'm sure there will be lots on the web to confirm or deny that! For many houses with existing radiators, especially where the pipes are larger than micro-bore, air to water will be a better fit. You also get domestic hot water - which I don't!😉

@ArborealTechie could you trim lower branches to let winter sun scoot in?

@rood Thanks, but the tree is around 50 meters from the array, so it's the whole upper canopy and trunk that shades the panels. I would need to reduce the height by around 50% to make a significant difference. The tree is over 50ft in height. With modern tractors becoming ever larger and farmers anxious not to damage them many trees in my area have been reduced to totem poles, which saddens me. I want to protect all my mature trees.

BTW, I use Home Assistant (as well as my own software) to monitor and control my system. This is how my display looked when the sun came out one day last year. I turned on the heat pump to reduce the charge going into the batteries, which were charging at 15kW. EV was also charging at 2.2kW (to prolong battery life). @X31Andy you can see the individual strings here.
#solar #electric #HeatPumps #EVs

Petrichor ᚄᚔᚅᚐᚁᚆᚃᚒᚔᚂ 19h ago

@ArborealTechie How many PV did you add?

@sinabhfuil There is 4kWp on the house (17 x 235W) and 21.6kWp on the shed. But the total that can be supplied by the inverters is only 10.5kW. Though I could potentially use 10.5kW in the house and charging our EVs, while still putting over 10kW into the batteries.

Petrichor ᚄᚔᚅᚐᚁᚆᚃᚒᚔᚂ 19h ago

@ArborealTechie How many panels is that?

@sinabhfuil There are 54 400W panels on the shed and 17 235W panels on the house.

Petrichor ᚄᚔᚅᚐᚁᚆᚃᚒᚔᚂ 7h ago

@ArborealTechie So many! 😂 Engineer came and looked at my place and said, nah, it'd only fit 5 panels, not worth it!

@sinabhfuil Anywhere you can put a south facing shed?😉