Integrated Combined Energy Management

Our energy is generated on site with the highest efficiency and conservation, and stored electrically and thermally to be used year round. Efficiency is further managed and enhanced with a service tunnel that allows easy and visual connection of all systems, ensuring high integration, quality maintenance and upgrade capability is built in, while obsolescence is designed out.

Electrical Demand

This is difficult to accurately predict as we will have variable occupancy in the four lodges and the variety of guests will use facilities in different ways.

Heating, Cooling & Ventilation

Space heating requirement in the lodges will be minimal, if any, due to the insulated high thermal mass, solar gain and residual heat from occupancy. However a radiant heating/cooling loop will be installed in the floor just in case it is needed on occasion. We considered earth tubes for cooling ventilation but were concerned about unlikely but potential bacterial issues. However on sunny days our solar PV will be running heat pumps to charge the thermal store, allowing free cooling capacity at the same time. Natural ventilation will also be built in, with heat recovery via a heat exchanger to the GSHP.

Solar Gain

The lodges are positioned in a gentle arc facing south, and all feature a sun terrace with an insulated roof and large rooflights (with blinds). This provides user variable shading in the summer and maximum daylight in the winter. The high thermal mass floor can absorb any warmth from the sun during the day and release it in the evening. Excess heat can be harvested by the heat pump and dumped in the thermal store, ensuring a comfortable environment at all times.

Solar Thermal

The sun terrace roof has prime exposure to the sun and will include integrated solar thermal loops that can directly harvest heat to the thermal store, or indirectly via the heat pump. We will also integrate solar thermal coils within the parapet roof between the rows of solar PV panels, however these will only harvest in the summer as they will be shaded in the lower winter sun.

Solar PV

30 PV panels (3 rows x 10) are within each lodge roof, south facing at 20° inclination. A further 44 panels may be placed on the barn roof, in total providing up to 40,000kWh per year.

Heat Pumps

A ground source heat pump (GSHP) is positioned between each pair of lodges, supplemented by an additional fan coil within the parapet roof to harvest ambient air temperature. A small air source heat pump (ASHP) is also positioned in the service tunnel. In combination when there is any spare solar power they will work to harvest every available source of heat within the lodges and service tunnel and store it in the thermal stores.

Masonry Stove

A double sided cast iron insert multi-fuel stove will be built into rammed earth with suitable expansion joints to prevent any cracking issues. The system will promote secondary combustion and masonry heating. A closed loop water boiler is incorporated for DHW, and a pizza oven is positioned immediately above the flue for cooking on the sun terrace.

Electrical Storage

A bank of electrical storage batteries is positioned in the service tunnel. Flow batteries are a new technology that seems particularly applicable, and will be investigated.

Thermal Storage

A pair of huge underground 1000+ cubic metre thermal energy stores (TES) are positioned between the lodges and the swimming pond. With the ambient ground temperature around 10°C we hope to drive the TES up to 40°C by autumn so that energy can be used in the depths of winter to deliver hot water via the heat pumps. In addition each lodge has a large thermal store tank kept to around 60°C that will heat DHW as it is drawn, so there is no separate DHW cylinder.

Idyll Energy Challenge

We have devised an integrated energy system for the site that allows us to be off-grid all year round. We challenge the wider informed community to review, analyse and put forward ideas to ensure the entire system is as good and efficient as it can be.


All our water is harvested on site from rainwater and borehole, it is used and reused, then processed on site, cleaned and safely returned back to the landscape.


A full water treatment plant is planned, and its clean outflow will be doubly processed by a small reed bed. Grey water treatment will also be used to reuse bath and shower output for toilets and irrigation.