20 Hunters Moon-Open Eco-Homes Factsheet 2014

20 Hunters Moon-Open Eco-Homes Factsheet 2014

Solar PV system

The system has a specialist inverter designed to minimise the impact of shading.  The inverter is linked to the internet so Totnes Energy can remotely monitor the system and are warned if there is a problem with any of the panels.  The panels are Yingli 250 which came 5th out of 151 panels, in terms of performance, in independent testing in Germany.

Solar PV switch

This Immersun device checks to see if there is any energy being sent back to the grid.  As soon as any energy is detected, it is automatically diverted to heat our hot water using a standard immersion heater.  The controller can also be used to control other devices as well such as towel radiators or panel heaters.  If you have two immersion heaters it can be used to heat the top immersion heater, and once hot, is diverted to the lower immersion heater.  This ensures the best use of energy, particularly useful in the winter months when there is limited solar PV energy.

Solar thermal system

This is a 12kW system, large enough to heat a small swimming pool.  It has been oversized so that the energy can be used to provide hot water and also contribute to heating the home.  The panels are Schuco, which are one of the highest performing flat plate collectors.  They even beat most of the evacuated tube collectors in terms of efficiency, yet have the benefit of the simplicity and longevity of flat plate collectors.

Biomass system

Totnes Energy installed a Windhager 15kW boiler under the non domestic Renewable Heat Incentive (RHI).  It qualifies for the non domestic RHI since it is classified as a district heating system since it heats more than one property.  We will receive approximately £30,000 in income against and installation cost of around £15,000.  More importantly, from an environmental perspective, we have managed to reduce our gas consumption to cooking only.  We have a manual pellet feed system with a 200kg hopper which we need to fill with pellets every other week in the winter.  The boiler needs an annual service which includes the annual emptying of the ash container.  In the spring, summer and autumn the boiler will be switched off since the solar thermal and PV system can take over.

Thermal store

We have a 500L thermal store which stores the energy from all of the renewable energy systems.  We have a PAW external heat exchanger that provides instant mains pressure domestic hot water.  This allows the temperature of the thermal store to be low without any concerns about the legionella bacteria.  The thermal store also allows the store to be kept at 85 degrees, whereas a standard cylinder is normally kept at 60 degrees.  This allows us to store more energy from the renewable energy systems.

Direct to radiators

The heating system is "direct to rads" which means each radiator is on its own heating circuit.  This allows every room to have a programmable room thermostat.  This means we can easily reduce the amount of energy used and unused rooms are not heated.

Heating system

The heating system is also low temperature with a designed flow temperature of only 45 degrees (typically 70 degrees for gas boilers with radiators).  This is achieved by the use of oversized triple Stelrad radiators.  This means we can make the most of solar thermal energy for heating in the marginal months in spring and autumn.

Wood burners

We installed a Burley wood burner which is the most efficient wood burner in the world at 92% efficient.  It also means that the burn is so complete, the ash tray very rarely needs emptying.

Floor insulation

We originally had solid concrete floors throughout most of the building so digging them up was costly.  We therefore installed 25mm of Celotex throughout.  This did cause issues with levels throughout the house, but these issues were overcome by our very recommended builder, Chris Noakes Construction.  Where we had suspended floors we installed 200mm of Celotex between and under the joists.

Wall insulation

These were already filled by the previous owner.

External wall insulation

Part of the new walls have Foamglass structural insulation blocks which stop cold bridging from the walls going down through the foundations.  The Foamglass is linked up to the underfloor insulation so that there are no cold bridges.  Foamglass is like a standard breeze block, but is exceedingly light and very strong under load.  We have 100mm of external polystyrene insulation.

Loft insulation

We increased the loft insulation to the now standard 300mm.

Damp issues

The extra levels of insulation and air tightness has caused damp issues throughout the property.  Our original plan was to install a positive pressure ventilation unit (Dampco in Brixham install these and they are very effective) or heat recovery system.  However, the biomass boiler and wood burners, which both have internal air supplies, have largely stopped this issue.

 

Battery backup PV system

The entire house is wired as a radial circuit rather than a ring main.  This is to future proof us so that certain circuits can be controlled when using battery energy from the PV system.  It is exciting to hear that the SMA battery backup inverter was released in the UK market last week, which will allow the easy installation of battery backup PV systems.  Also the SMA offgrid inverter can now be installed as part of a grid connected system, so you can use your own battery banks.

Lighting and electrical goods

All of the lighting is LED and the electrical goods are A++ rated.  The fridge/freezer can run for 24 hours without requiring electrical energy.  This means that it can be put on timer so that it only runs during the day when there is plenty of solar energy.

The future

We plan to go offgrid in respect of gas and electricity.  We will also start to look at reducing our water consumption.