Solar heating for schools

By - , Build 108

BRANZ recently initiated a year-long trial in three schools of a simple space heating system that makes use of otherwise wasted heat.

Fairfield College solar wall construction (note weather station on middle of the roofline).
Solar wall detail of pyranometer on wall face measuring solar radiation (i.e. solar energy).

The heating system uses the warm air naturally generated within the cavity space directly behind dark coloured long-run steel cladding. The warm air is drawn mechanically into a simple ducting system at the top of the wall and exhausted into the adjacent room. A smart differential temperature control is used to determine when the warm air should be drawn in.

Solar walls the key

These ‘solar walls’ have been retrofitted to one classroom in each school. While a matt black would have been the ideal colour from a thermal perspective, dark greens have also been used to match existing school colour schemes. Serendipitously, these north-facing walls are most effectively heated in the colder months as sun angle is at its lowest.

Although the functions of the classrooms vary – a maths room, a weights room and a library – the solar aspect and solar gain potential of each is relatively good. Practically, the room function and solar aspect are the most common restrictions in applying this technology to retrofit situations.

A partnership project

BRANZ is working in partnership with the Enviroschools Foundation (a nationwide wholeschool approach to fostering sustainable schools) and the three secondary schools, as part of this trial. The schools, each representing a different climate zone, are Northcote College (in the Auckland region), Fairfield College (in the Waikato) and Aurora College (in Southland).

Fairfield College solar wall construction (note weather station on middle of the roofline).

The project has a number of components to it, including looking at:

  • practical issues, such as the buildability of the system
  • heating efficiency issues – the amount of incidental heat actually captured
  • energy flow issues – the energy required (for powering the control systems and fan unit)
  • indoor air quality issues, from the intake of the warmed cavity air
  • educational issues, in the development of a school educational resource around the project for students
  • weather data collected in addition to system data.

A similar technology is being used overseas to heat indoor spaces, but it is considerably more sophisticated. One of the objectives of this research is to compare the performance of a simpler system using off-the-shelf technologies and building materials, which is more accessible to all.

Solar wall detail of pyranometer on wall face measuring solar radiation (i.e. solar energy).

This simple low-energy technology has potentially wide applications for various building types. Already, BRANZ has successfully used this system in a domestic situation (see Build 94, June/July 2006, pages 32–33) of which the lessons learnt are being applied to this new research.

For more

A follow-up Build article will detail some preliminary results.

Download the PDF

Articles are correct at the time of publication but may have since become outdated.

Fairfield College solar wall construction (note weather station on middle of the roofline).
Solar wall detail of pyranometer on wall face measuring solar radiation (i.e. solar energy).

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