The Solar House
THE SOLAR HOUSE SERVES AS LIVING TESTAMENT TO THE FACT THAT ZERO CARBON BUILDINGS ARE A PRACTICAL AND AFFORDABLE REALITY. CAMERON: IF YOU’RE READING THIS, THIS IS HOW IT’S DONE
Home » The Solar House
Published: 12 March 2014
This Article was Written by: Katie Hill - My Green Pod
The five-bedroom construction sprawls across 360m² of Great Glen, Leicestershire, and incorporates technology that allows the offset of 100% of its energy requirements using on-site generation. Electricity will still need to be bought to run the heat pump when there is no light for the panels to generate electricity, but this will be offset by the energy sold back to the National Grid. This means running the house should be cost neutral — in fact, with the relevant subsidies in place, the lucky owner should be in a cash positive position.
Newform Energy sees the technology used as a viable alternative to heating and powering homes through traditional fossil-based energy sources. Data from the building is being gathered and analysed independently by De Montfort University, and the evaluation is crucial to the credibility of both the project and the science behind it.
The Solar House cost about £550,000 to build, and the additional cost of the technology — over and above what would be used in a conventional house – is around £45,000. ‘This makes it around 5% more expensive than the average selling price for a similar-sized property in the area,’ says Newform Energy, ‘which isn’t far off stamp duty.’
‘Stealing energy from precious resources with little regard for the consequences is a short-sighted and risky approach. We have an abundance of sustainable energy; learning how to tap into it and developing a unique approach could revolutionise our ability to deliver zero carbon buildings.’
Anthony Morgan, CEO and founder of Newform Energy
The brainchild of Michael Goddard of Caplin Homes, the Solar House was intended to demonstrate a repeatable methodology for zero carbon buildings. For Newform Energy it was the final piece in the jigsaw puzzle: inter-seasonal energy storage in a cost-effective package, that could be deployed across the mix of high- and low-density development schemes. The symbiotic relationship between the different technologies means that the sum of the parts is greater than the individual components. Here’s how it was done.
The windows are triple glazed with a generous south-facing area. Newform Energy is also evaluating passive solar walls, which pre-heat the incoming MVHR (mechanical ventilation heat recovery) air and help with the overall energy equation.
Water-to-water heat pump
A water-to-water heat pump is a device that transfers low grade thermal energy from a source, such as the ground, to a higher temperature destination, such as a DHW cylinder.
The device uses a compressor to take the low grade heat, then applies mechanical work to raise the temperature so it can be used within a building. It’s similar to a fridge working in reverse: the cold part is the part in the ground and the hot element, like the one found at the back of your fridge, is used to heat the building.
The conventional timber frame has low embodied carbon, as well as being a much better insulator than mineral-based alternatives. The base level of insulation (100mm) sits within the studs of the frame, which keeps wall thickness down.
In order to attain the required u-values (the measure of heat loss for a particular part of a building — a lower value means a more efficient transfer of the building’s heat), multi-foil cladding (as opposed to more foam insulation) is used between the studwork and the service void.
This means that, with its larch cladding, the walls of the Solar House are only 250mm thick, yet have a u-value of 0.14. Current building standards (Part L) place the maximum u-values for walls at 0.3.
The smart controller calculates energy flow, working in a slightly different way from either a more conventional differential controller (such as a solar controller) or a BMS (Building Management System). In essence, it calculates the amount of energy required to hit a target within a given time frame.
It then works out, from the resources available, the most efficient place from which to draw energy — always prioritising free power.
Foundations – the thermal battery
‘Historically, the best way to achieve a zero carbon build was to use a hybrid system with deep boreholes, from 35-100m, and a heat pump’, says Anthony Morgan, CEO and founder of Newform Energy. But this approach is fraught with issues — the main one being geology. ‘No matter how good a geological survey, when you start to drill you don’t know what you will find’, he says. ‘The Solar House takes our existing methodology and does away with the need for deep boreholes, using the foundations beneath the building (which are only 1.5 meters deep) as a thermal battery instead.’ This removes the need for deep drilling and large horizontal ground arrays.
Provided the house is highly airtight and well insulated (Newform Energy has its own minimum standard, somewhere between Passivhaus and building regulations), a formula can be applied to calculate the thermal storage requirements, heat pump size and number of PVT panels needed on the roof.
In summer months, if the PV-T (photovoltaic-thermal) panels are hotter than the domestic hot water (DHW) cylinder (which stores hot water for potable use), free solar thermal energy passes to meet demand. If the panels are hotter than the ground — but not hot enough to heat the DHW cylinder directly — the panels are used as a source for the water-to-water heat pump.
If the building demand is satisfied, the building temperature is 21°C and the demands of DHW have been met, then the excess energy from the panels is directed to the earth energy bank beneath the building. This energy is then stored inter-seasonally and used to heat the house during winter, when there is less energy from the sun to meet the building’s demands. The process allows the heat pump to run less and, when it does, to run more efficiently. This adds up to a higher efficiency (COP) than conventional heat pumps.
Additionally, the cooling effect on the photovoltaic part of the PV-T means more electrical generation per kW peak than conventional PVs of the same output.
Newform Energy doesn’t just focus on new builds, and Morgan believes the retrofit market could benefit most from a hybrid approach. Its retrofit solution offers massive carbon savings while also being cost-effective; the soon-to-launch ‘multi-source air source heat pump’ has an additional energy input that takes low grade solar energy during the winter months to improve overall system efficiency.
Using this method, Newform Energy has been able to meet the government’s 2050 energy targets — an 80% CO2 offset on all buildings in the UK – today, provided insulation, glazing and other thermal efficiency measures have been carried out on the house. Though targeting off gas grid homes, Newform Energy hopes to introduce products that will be able to show a similar impact on gas grid homes in the future.
The target price for this system, which will take care of 100% of a home’s heating requirements and around 60% of the home’s electrical energy needs, is roughly £14,000, including installation. When you take into account the financial incentives of the FITs and – hopefully – the RHI, this could dramatically reduce a home’s domestic power bills, and would typically pay back in under six years.
If you’re looking at ways to improve the energy efficiency of your home, the first thing you should look at is insulation. It’s the cheapest and most efficient means of carbon and cost reduction, and it’s always best to look at ways to reduce your energy consumption before you consider generating your own. ‘There is definitely a crossover point,’ says Morgan, ‘where the costs associated with extreme insulation and air tightness measures can be better applied to generation in order to get maximum cost benefit and CO2 offset.’
For more information on Anthony Morgan and Newform Energy’s projects, visit its website.