Rooftop Hydroponic AND Fish Farm anybody ? had an article on this prototype system that combines hydroponics and a fish farm into one unit for all year round veggies and a few fish.

The prototype Globe/Hedron “is a bamboo greenhouse designed to organically grow fish and vegetables on top of generic flat roofs. The design is optimized for aquaponic farming techniques: the fish’s water nourishes the plants and plants clean the water for the fish,” according to designer Antonio.

UK Government delay Feed In Tariff Cuts

At yesterdays Green Building Event at the Eden Project the news came through (Tweet feeds) that Greg Barker, the UK government energy and climate change secretary tweeted:

“Having listened carefully to industry, we are looking at scope for pushing back a little the next proposed reduction in the solar tariffs.”

They were due to be cut in July from the current 21p per Kw.

If you have / get solar panels there are several return on investment streams:

  • Generation tariff – your energy supplier will pay you a set rate for each unit (or kWh) of electricity you generate. Once your system has been registered, the tariff levels are guaranteed for the period of the tariff (up to 25 years) and are index-linked. For a full list of generation tariffs, see FIT payment rates published by Ofgem
  • Export tariff – you will get a further 3.2p/kWh from your energy supplier for each unit you export back to the electricity grid, so you can sell any electricity you generate but don’t use yourself. This rate is the same for all technologies. At some stage smart meters will be installed to measure what you export, but until then it is estimated as being 50% of the electricity you generate (so that if your solar PV system is less than 30kWp you do not need to have an export meter fitted)
  • Energy bill savings – you will be making savings on your electricity bills , because generating electricity to power your appliances means you don’t have to buy as much electricity from your energy supplier. The amount you save will vary depending how much of the electricity you use on site.

One of the Eden Project show talks had these figures, that may be high end in terms of them being from a chap that is from a PV installation company.

The Energy Saving Trust has figures of:

A typical domestic solar electricity system with an installation size of 3kWp could earn:

  • £530 a year from the Generation Tariff
  • £40 a year from the Export Tariff
  • £100 a year reduction of current electricity bills

Scaling this up to a 4kWp system that’d be £893.

Being fair to Tony at Cornwall Solar Panels (Tel 01872 562 775) who gave the above figures, his entire talk was centred around there being no such thing as the best solar panel, but the best solar panel configuration for a particular situation. Panel efficiency, shape, size, drop off with heat, drop off with shading, the roof angle and a bunch of other variables (string or per panel inverters) all influence the efficiency and the system cost and so the Return On Investment (ROI). His talk went over about a dozen different installations they’ve done and have figures from. The clear implication / impression is that they are doing installations all over Cornwall.


UK Solar Hot Water Trial Findings

The Energy Saving Trust did a survery on a large number of UK and Republic of Ireland solar hot water systems.

PDF report on the survey >>

Key Points

  • There were 54 flat-plate systems in the trial.
  • There were 34 evacuated-tube systems in the trial.
    • There was no difference in the annual solar energy yield observed between solar installations using flat-plate solar collectors and those using evacuated-tube solar collectors. This may be because although evacuated-tube collectors have higher insulation, flat-plate solar collectors generally have a larger working area as a proportion of the collector size.
So there are none of the “new” Thermodynamic Panels in the survey. These do appear to be different and better. Providing 24 hour hot water.

Distribution of the surveyed / trial locations:

So for Silver Spray in Cornwall, should get better results as more sunshine:

The solar energy input to the hot water cylinder is at a maximum in summer, with back-up heating providing more energy in the winter months.

It’s key to set the backup (non solar) heating system to run so that the solar heating can be most effective and the house occupants have hot water when desired.

How to improve the performance of a solar water heating system:

  • Using boiler timers and/or solar controllers to ensure that water is only heated by the back-up heating sources after the water has been heated to the maximum extent possible by the sun.
    • Timing of back-up heating and hot water use. Systems
      provided more energy when the back-up heating was
      used just before the main hot water use or at the end of
      the day. This provides a better opportunity for the solar
      collector to heat the water rather than using the back-up.
  • Having an adequately sized dedicated solar volume (that is, a portion that can only be heated by the solar water heating system). Where a dedicated solar volume is not used (for example in systems that do not require the existing cylinder to be changed), the timing of back-up heating has a particularly important impact on performance.
  • Insulation is a vital part of this, as systems with poorly insulated storage cylinders can suffer from inadequate hot water provision in the mornings.

Key Findings:

  • Well installed and properly used systems can provide around 60% of the years hot water.
    • Across the whole trial, the proportion of domestic hot water energy provided by solar power ranged between 9 per cent and 98 per cent (with a median of 39 per cent).
  • Plenty of other findings, see the report.

Customer / Consumer Advice

What to expect from your installer:

  • All MCS installers should be able to provide a detailed breakdown of the specification and costs of their proposed system. They should:
    • Complete a technical survey.
    • Explain how they calculated the size of the system to be appropriate for your hot water usage.
    • Provide an estimate of how much heat will be produced by any proposed system.
    • Supply clear, easy-to-understand and detailed information and advice on how best to use the system and operating instructions.
    • Explain how the system will be installed and if there will be any disruption to your property.
    • Install and set controls and settings to ensure you get the most out of your solar water heating system.
    • Provide clear and easy-to-understand information on product and workmanship warranties.

EcoBuild: Thermodynamic Panels (Heat Exchanger)

Thermodynamic Panels

These black panels were on display:

These black aluminium panels have refrigerant fluid pumped into them. The heat absorbtion of the black panels changes this to a gas, that is sent to a compressor, which releases heat energy in the heat exchanger where the heat goes into the water. The gas then goes through an expansion valve, putting it back to a liquid before it goes back to the panel. (See explanation & figures below forum comments below).


  • 55 degree C water output.
  • Can provide 100% of hot water and heating, 24/7, 365 days a year.
  • Works day or night, as it absorbs heat energy from the atmosphere. It is presumeably helped when it’s sunny !
  • Works when temps are down to -15 degrees C
  • Can be wall installed, which would work well for the Silver Spray proposal.
  • Co-efficient (COP) rating of 4.5 to 7.
  • Distributed by Jewson.
  • 1 panel system (with the boiler and reverse refrigeration bits) is about £4,500.
  • Can have multiple panels in a “toast” stack. Expo figure for that was about £6,500.

Forum Comments:

  • “Looks like it’s a heat pump with a solar-assisted air to liquid heat exchanger on the outdoors end.” seems to sum it up pretty well !
  • “depending on the heat pump, it’ll be better (better COP) than an ashp in sunlight, but probably worse at night unless there’s much wind to move air across it, although it will have a bigger surface area than in most ASHP’s which will compensate for this to some extent. “
  • “It also has the advantage of not needing (potentially noisy) fans”

Also from the forum, from their N. Ireland distributor:

The system is not new technology; it is basically a freezer “in reverse” and like a freezer consists of a heat collecting panel(s), refrigerant piping and an integrated electric heat pump.  It is a clever application of well tried and tested technology that has been around for almost 100 years.  The panels are made from weather protected anodized aluminium and are not vulnerable to extremes in hot or cold. They are light, weighing only 8 Kg and may be mounted in virtually any orientation or angle.  It has been estimated that 25% of the energy absorbed by a panel comes from solar irradiation, the balance taken from air and rain. Both sides of the panel are available to collect energy. The company that manufactures the system is based in Portugal and to meet growing global demand they have just built a second factory reflecting their 25 year history of success with the product.

You can check them out at

The Energie system is fully scalable from 1 – 2 panels for domestic hot water, to 4 – 24 panels for central heating right up to 40 panels for large volume hot water requirements. Note that additional panels simply mean faster water heating times, not higher water temperature which is set to between 55 and 60 C maximum.  A typical domestic installation for domestic hot water will have a 250L cylinder with a single panel mounted on the roof.

The heat pump is integrated directly into the Energie cylinder so an existing hot water cylinder cannot be used in this configuration. For central heating and large volume hot water requirements the heat pump (Solar Block in Energie speak) is a stand-alone device. Energie cylinders are either stainless steel or enamelled steel and can come with an additional coil for connecting into a backup heat source if desired. Sizes range from 200L to 6,000L.

All Energie Thermodynamic Systems are accredited under the MCS scheme.

The system uses 407A refrigerant and doesn’t need topping up. The only maintenance may be the occasional replacement of the sacrificial anode in the cylinder should you live in an area with soft water.

Another point raised concerned the panel frosting over in winter. This is possibly best addressed by personal experience.  I installed a 300L single panel system in my home at the start of this year, and although there was some frosting in the very cold weather at that time on the top surface of the panel, the bottom side was clear, and we always had enough hot water. Eight months later we have never had call to revert to either our central heating boiler which has been turned off these past 5 months, or the small integrated immersion that comes with the Energie cylinder. I estimate from measurements I have taken that the Energie system has used an average of 3.6 KWh of electricity per day over the 8 months January to August for our 4-person household at a COP of just over 3.

Hundreds of Energie systems have been installed successfully throughout Ireland over the last 4 years and having come through last winter are well tested for the vagaries of the UK and Irish climate.

Finally some additional information as supplied by Energie can be found using the link below.

More Information from ThermoGroup


1. Aluminium Panels
Refrigerant fluid circulates through the panels and absorbs heat energy from the atmosphere. This increase in temperature changes the fluid into a gas.

2. Compressor
The gas then passes through a compressor and the temperature increases.

3. Hot Water Cylinder
The hot gas then flows through a heat exchanger in the Thermodynamic Block which transfers the heat into the water, which can be used for sanitary hot water, space heating or larger applications such as swimming pools.

4. Expansion Valve
The gas then passes through an expansion valve, reverts back to a liquid and flows back to the panels to
repeat the process.

Figures for Thermodynamic Atmospheric Energy Panels

I read or heard at the show, that increasing the number of panels increases the speed at which the system works. So I think you could add a panel to make the system work faster at grabbing the optimum conditions? (Need to ask them)

Air Source Heat Pump Vs Thermodynamic Atmospheric Energy Panels:

 Air source heat pumps  Thermodynamic
• COP of around 4
• Outputs of 6-18kW
• Outdoor noise pollution
• Requires regular maintenance
• Efficient to just below 0 degrees C
• Fixed sizes
• Fan assisted, low active surface area
• COP of up to 7
• Outputs of 1.7 – 53 kW
Silent outside
• Only one moving part
• Works down to -15 degrees C
• Total flexibility
• Active surface area of 3.2m2 per panel
 Standard Solar Thermal Panel  Thermodynamic
• Provides up to 70% of your hot water
• Must be mounted south facing for best results
• Needs backup from a boiler or immersion heater
• Needs sunlight – low performance in winter/night
• Can only assist central heating
• Fragile glass panels
• Provides up 100% of your hot water.
• Can be mounted south/west/east/north on a wall
• No backup required – Not connected to boiler
• Works in the dark and down to -15OC – 24/7
• Can provide 100% of your central heating
• Aluminium – tough, long lasting, anti corrosive
They can work on a north facing wall, but work best the more direct solar exposure they get.

Case Studies and Cost

Running Cost:


  • 4 bed house, one panel & 280 L cylinder, for hot water only = £109.50 pa
  • 3 bed house, 6 panels & thermodyanmic block for central heating only = £346.75 pa

So how much would a central heating and hot water system cost per annum ?
– those figures have an assumed electricity tariff of £0.14/kWh. If the system is part driven by my own solar panels, the cost would be reduced (although you need to factor in the capital cost of the solar panels.)

Purchase Cost:

Need to add in the cost of having it all installed and signed off to the level that’ll hopefully get the Renewable Heat Incentive.


Thermodynamic kits ship pre-gassed, ready for installation and include the following:

  • Thermodynamic Panels/s
  • Panel Fixing Kit
  • Hot Water Cylinder with Thermodynamic Block
  • 30m Copper Pipe
  • 30m Low-loss Lagging

The above thermodynamic kits are suitable for supply of sanitary hot water in domestic applications. Thermodynamic systems for Ambient heating or larger applications require a more detailed specification to ensure we provide you with the right solution.

I’ve emailed them for a rough quote.

EcoBuild: Solar Panel Angles

There may be a problem with the current Silver Spray plans and the angles for the solar panels. The current plan is for the panels to be bolted onto the proposed flat roof at the back.

  • Solar panels should be south facing and between 20 and 60 degrees.
    • I’ve heard / read that the ideal angle for solar panels in Cornwall is for them to be at 30 degrees (and south facing).
    • Below 20 degrees panels don’t self-clean when it rains. Dirty panels are less efficient
    • The angle that solar panels are normally mounted on flat roofs is usually low to reduce the amout they can get grabbed by the wind and ripped off the roof !
    • It could just be that a framework for the panels is factored into the building so that there is no chance it can be ripped off by the wind.
    • Flat roof mounting systems for panels all seem to be at about 10 degrees, so that the gap between panels is around 38 cm, and so that their is reduced possible “wind load”
    • Current rear flat roof area is about 4.1 x 8m = approx 32.8 sq m. If panels are all flat, a 4kW system takes about 28 sq m. So will need to see how the space works out.
    • See – images below – gap between panels moves up to 1.36m from 0.38m as solar panel angle of tilt changes from 10 to 30 degrees. But see reasons below for wanting 20 degrees or more tilt.
    • The Energy Saving Trust matrix for PV angle of tilt and how much south facing, that suggests optimum is south facing and between 20 and 30 degrees tilt.

  • More vertical panels do better in the winter, when the sun is lower in the sky. You are more likley to want more hot water in the winter (for space heating) and more electricity generation (to power feed the air source heat pump). BUT only 10% of generation output will be in the winter, so best to angle the panels for max, over the year, output.

I ran figures through the Energy Saving Trust calculator for a few variations at the Silver Spray postcode location:

  • South slope, XLarge 4Kw, 90 degrees = 2,688 kWh pa
  • South slope, XLarge 4Kw, 60 degrees = 3,499 kWh pa
  • South slope, XLarge 4Kw, 50 degrees = 3,643 kWh pa
  • South slope, XLarge 4Kw, 40 degrees = 3,716 kWh pa
  • South slope, XLarge 4Kw, 30 degrees = 3,715 kWh pa
  • South slope, XLarge 4Kw, 20 degrees = 3,640 kWh pa
  • South slope, XLarge 4Kw, 10 degrees = 3,492 kWh pa
  • South slope, XLarge 4Kw, 0 degrees = 3,274 kWh pa

EcoBuild: Photovoltaic, PVT Vs PV or PT

Photovoltaic Thermal:: EcoBuild Expo Update

At the Ecobuild expo, there were a LOT of companies who had photovoltaic elec or water heating systems.  Few were combined PVT (both electricity and heating water). So I started asking why. Speaking to those that make the panesl and installers / advisors the consistent reply was that the reduction in output of both systems was more than 50% down on what you’d get if each was stand alone. One company that produced PV and PT panels said that:

  • A PV panel could produce around 280 Watts  of elec, a PVT panel about 120 Watts
  • A PT panel over 200 (I think degrees) water, but only 40 degrees from PVT.

Yes, it’s still good to cool down PV panels, with ventilation, or even surrounding green roofing. But it seems that cooling them, by linking in pipes to generate hot water doesn’t work. It seems that the temp hot water panels work at is so high to be efficient, that takes out too much electricity production. Or you compromise the amount of hot water production by having the panels at a much lower temp. ie to be efficient they both operate at vastly different temperatures.

So that means looking at seperate systems for electricity production (PV), hot water productin (PT) and something for when the sun isn’t shining for hot water (for taps and heating).


Portloe house visit

Today, Robert from ra-studio, took to visit a house in Portloe that he worked on before he set up his own practice.

Rob, post visit dropped this in an email to me:

I hope you found the trip over to Claire’s place useful yesterday – it’s sometimes good to experience spaces in a more physical sense / situation, and perhaps helps you to visualise how some of your spaces could feel. I think there are obvious parallels between Sea House and Silver Spray (connection / views / relationship with the sea), and seeing how it has been handled there, I hope was helpful for you.

Yes, well worth the visit. It was fantastic to meet such an obviously happy client (and her cool, crazy young dog, Zola).

Their project was serialised in the Telegraph:

So many things about the house, that I hope to include in Silver Spray. The feeling of space, the flow through the house, the views, the natural materials ……

The house looks over the village and was designed to fit into the slope. Without the red circle, it’d be a chunk less obvious !

You drive up the drive and see the studio on your left with the house a bit beyond.

The cladding on the studio is the same as on the house, but it hasn’t yet worn to the same more grey colour / tint.

The house has an amazing central “spine” so that as you walk up to the front door, you see through to the view.

Although the stone detail of the wall below the cladding looks stunning on this house, it’s not something I feel will work for Silver Spray. Except !!!!! maybe for the rear wall of the courtyard. Well something needs to go on that wall. Perhaps it’ll be a retaining wall held back by Gabions (steel cages of rocks). But a quick on-line search suggests the life of Gabions, which is down to the life of the steel holding them together is 50 to 60 years. I suspect less in Silver Spray site, so close to the sea. Damn, as they’d be great.

The slate flooring runs from around much of the house, straight into the house, where it’s apparently super easy to clean. The texture it gives was fantastic. The same slate was used for the external window sills.

Almost all of the windows are by Velfac, with thin profiles, nice colours etc.

This upstairs window has a piece of glass over the front to create a “Juliet Balcony”. Which will work great for the second bedroom.

I’m still not a fan of the idea of wooden decking. Here there was a mixture of slate and wooden decking.

Coat room to the left as you walk in 🙂

Lovely doors, floor and wooden stairs:

Nice detailing on this sliding door that can close over the entrance to the kitchen.

Wide, light floor boards. Interestingly, wooden floors upstairs. I was thinking carpet, but this did work well. OK they have light coloured tiles in the bathrooms upstairs. The bedrooms had good integrated storage.

The above white TV makes it less dominant on the room. Also a superb idea that it pushes against the wall, but is on an arm that can come out and so be viewed from the seating etc. This could be a great idea for in any bedrooms. Although I’m not planning TVs in the bedrooms, it’d be good to allow this future option.
Having a TV in the 2nd bedroom for guests could be a nice touch.

Pebbles in a gulley outside the door, to prevent splash up from rain onto the windows and also to drain away water flowing down the windows.

A photo from when the studio was being built:

The house has solar heating and solar electricity.

Light and ventilation tunnel ?

With the stairs going from the floor of the house, to the top and being capped by a sky-light, and also a south facing window (or two) at the top of this “column”, I was reminded of the Potton Lighthouse, with it’s “wind catcher / light funnel”.

I’m wondering if these windows could be an automatic, intrinsic way that the house heats and cools itself down?

Below is a screen shot from a PDF about the Potton Lighthouse.

Photovoltaic Thermal (PVT)


  • See this post on Photovoltaic, PVT Vs PV or PT.
    – it seems that PVT just doesn’t yet work, and may never work as they have very different optimal temperatures.

Photovoltaic Thermal (PVT) with New Form Energy ?

In late Feb 2012 I dropped an message to (via their on-line enquiry form) for a call to chat over the Silver Spray project.

  • Saying that  the current plans (pre planning application) have allocated a 8 x 5 m (approx) flat roof area for solar panels.This is on the south facing side of the building. The long north to south edge is just over 8m, the short edge is just under 5m (about 4.8m).
  • I’ve not had a reply / response and that was almost a month ago. Not ideal. OK I know a single email from their site form could get lost but ……

Origional Post:

Photovoltaic Thermal (PVT) is relativly new, but regarded as the most efficient at year round producing electricity and hot water.

” A well insulated 200m sq. house would need a 4kWp system costing around £20,000 installed, including a heat pump and hot water cylinder.” Homebuilding and Renovation magazine.

Supplier:, where they claim:

  • A drawback with Photovoltaic panels (PV) is that as the surface temperature of the panel rises, the output drops. PV panels typically lose efficiency of up to 0.5% per degree rise in panel temperature.
  • Solar thermal collectors for hot water can give little or no hot water when there is little or no sun.
  • Although heat pumps are potential greener than burning fossil fuels, they do still use large amounts of electricity.

So a combined system:

  • One panel for PV and thermal means that:
    • 1st the growing heat is drawn away from the panel
    • 2nd, less total roof area needed for same output.
      • The Hybrid Solar Solution, with PowerVolt panels installed on a UK house with 28m2 of available south facing roof area, will produce the equivalent annual electrical output from 38m2 of conventional monocrystalline photovoltaics. The same area of PowerVolt collectors will offset approximately the same amount of thermal energy as 8m2 of conventional solar thermal collectors (without any contribution from the heat pump). Using separate PV plus solar thermal systems would therefore require 46m2 to generate the same electrical and thermal energy produced by 28m2 of PowerVolt thermal collectors.In addition, with the size of solar installation referred to above, the heat pump can produce up to 22,000kWh of heat in winter months when the demand is highest.
  • Solar thermal+ heat pump, means that at night or when low sunlight, the panel can act as a thermal collector (not a solar collector). This, then via the heat pump generates hot water.


  • All year round solution
  • Significantly increases your electricity production
  • Fastest payback of all renewable heating systems
  • Low maintenance and user friendly
  • Solution that optimises efficiency, saves space and money.

The Potton "Lighthouse"

The Potton (now owned by Kingspan) Lighthouse project looks stunning.

I’m wondering if this could be flipped so the flat face has windows and faces the sea. Also make it thicker / deeper from front to back.

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