Solar evacuated tubes “Solar evacuated tubes are ideal for climates such as the UK’s as they are virtually unaffected by air temperature and wind-chill, with no noticeable variation in performance whether the ambient temperature is 0°C or 30°C. The panels incorporate horizontally mounted vacuum tubes with a curved collecting surface. The panels can therefore be mounted at the optimum angle yet still absorb the same amount of energy. Solar energy penetrates the glass and is absorbed by the specially selected coating on the collecting surface. Once absorbed the energy is trapped inside the tube by the vacuum. A unique aluminium insert helps transfer the trapped energy to the advanced internal manifold, directly heating the water and minimising energy losses.”

The design team identified solar evacuated tubes as the most appropriate source of renewable energy for the site. Solar hot water systems offer one of the best paybacks of all on-site renewable energy technologies.

Renewable energy stairwells
The proposed design is a solar pre-heated cold feed system to individual condensing boilers.  By pre-heating the water serving individual units, less energy is used to heat the hot water to the desired temperature.

This will achieve the 10% renewable energy contribution because the thermal performance of buildings constructed to Part L Building Regulations and the temperate UK climate mean that only 40% of the hot water used is for space heating and the other 60% is used to provide domestic hot water.

In developing a model solution, Baca was keen that the renewable energy source should be integrated with the architectural design, to contribute to the evolution of a new sustainable vernacular.

To achieve this and allow for future maintenance and plant replacement or retrofitting, the design team developed a system organised around the access to the flats. Individual arrays are mounted above the stairwell roof, providing hot water via communal hot water tanks to the six flats off the stairwell.

This means that all servicing and distribution for individual flats is contained within the stairwell allowing easy maintenance access and concealment of external piping from frost. The relatively short runs of piping means heat loss during distribution is kept to a minimum.
It is possible for a housing association/private landlord to supply the solar thermal energy communally without having to take responsibility for billing users for the energy supplied, because the energy generated by solar thermal is solely renewable and therefore no fuel costs are associated with the system.

The responsibility for energy billing for a small-scale development would have significant ongoing cost implications for a Landlord and would involve a strategic change to their business operations, which was not deemed commercially viable.

The stairwells have been designed to extend above the eaves line to provide an unshaded surface and clearly articulate the entrances to the flats. Preliminary calculations from evacuated tube manufactures indicate that the available roof area above the stairwells is ample to accommodate the required area of solar collectors to meet the 10% renewable energy requirement for each group of six flats.

The solar array can, if desired, be increased in size to deliver a higher proportion of renewable energy or to serve more flats. Furthermore the inclination of the array can also be tilted towards the sun to optimize performance efficiency. Should the angle of inclination be restricted through either planning constraints or costs then the solar evacuated tubes can also be employed vertically or horizontally with only a 10% loss in performance.

Each stairwell will also have its own mailboxes and visible numbering system to assist navigation and identification of individual dwellings.
Baca is further developing the stair core concept to integrate bicycle stores, recycling units and general waste, secure delivery areas and modular wiring systems or wireless networks to encourage working from home, thus reducing unnecessary journeys to the workplace.

baca (Barker And Coutts Architects)
Tel: 0870 750 2023
Email: mail@baca.uk.com

 

Baca's development project The street front, linear block and rear curved block, embrace a south-facing landscaped courtyard that opens onto the parkland beyond. The ribbon balconies provide natural shading and unify the development. Owners and tenants can enjoy the shared landscaping with the benefit of generous private balconies above the ground floor. An intensive green-roof system aims to make this a high quality sustainable development. The shared landscaping with the benefit of generous private balconies above ground floor. A green roof to provide additional habitat and also nestle the building into its semi-rural setting surmounts the building. The roof combined with a sustainable drainage system for footpaths and the carpark will also responsibly manage water on the site. Designed for the East Thames Housing Group, the scheme is designed to an Ecohomes ‘excellent standard’ and optimises low energy measures to be robust in operation and simple for residents to use. The mass of the building is orientated south to optimise solar gain and so that each flat has a dual aspect for natural ventilation.