The Green Building

Solar PV systems are extremely long-lived and require little or no maintenance. An example of this is the Green Building in Dublin's Temple Bar which had its solar electricity system installed in 1994, and has been benefiting from it since.

The Green Building's roof has a 3.2 kWp system made up of 72 poly crystalline, 50Wp modules, configured as two arrays of 36 modules. Each Solarex NMSX50 module has a guaranteed output of 47.5 Watts. This means each of the two arrays has a guaranteed output of 1710 Watts. Even now, in 2008, 14 years after they were installed, each array is still generating in excess of 1710 Watts, with no maintenance. A peak of 1804 Watts was observed on 21 June 2006.

About the Green Building Project

This unique building in the heart of Dublin’s Temple Bar has been designed to minimise undesirable heat gains and losses, and maximise the use of solar energy.

The project objectives were to:

1. Build a mixed-use building with extremely low energy requirements
2. Use recycled materials and materials from sustainable sources
3. Generate as much renewable energy as possible

1. The building

The build included:

• External insulation
• A relatively small windows-to-walls ratio
• Very high quality double and in some cases triple glazing
• No baths
• Very high efficiency light fittings
• No car parking (bicycles only)
• An internal court that closes over during cold periods, like the Cardiff Arms stadium, and opens up during warm weather to provide natural ventilation and cooling

2. Recycling

Recycled materials and materials from sustainable sources were used where possible in construction, and waste material is recovered and recycled during its ongoing operation.

3. Renewable energy

The building’s renewable energy systems have been continually refined and updated over the years. Energy sources include:

• Wind turbines on the roof
• A heat pump to heat the building in winter by extracting low grade energy from the underlying bedrock
• Solar hot water
• PV (photovoltaic) panels

The result

The building was completed in 1994. Among initial teething problems, the wind turbines were found to be uneconomical because of high operating and maintenance costs and noise problems.

But the solar sources have been a complete success. The annual output of the grid-connected system is 2,731kWh, and the value of the electricity it produces now exceeds the cost of all the electricity required for the heating systems.

The building exports surplus power to the national grid, and the PV arrays have required no maintenance during their first 12 years - apart from the replacement of three fuses after a violent thunderstorm.

From batteries to the grid

In the initial design, the roof-mounted wind turbines and PV panels charged a bank of heavy duty batteries.  Batteries have a limited lifespan of about 10 years, by which time it was anticipated that legislation would be in place to switch to  grid-connected inverter/controllers.

These have the great advantage of allowing the solar PV electricity generators to operate continuously at maximum capacity. When output exceeds demand, surplus power is exported to the grid.

Cool Power makes history

In 2006 Cool Power received its licence – the first of its kind in Ireland - from the Commission for Energy Regulation to connect small-scale renewable energy generators to the grid.  ESB Networks then installed its first ever small import/export meter in the building.

Cool Power commissioned the grid-connected system on 16 June 2006, and it has been in continuous operation ever since.

The savings

The estimated annual savings in energy costs from renewable sources after allowing for additional operating costs is £4,066 (€5,163). The additional cost compared with a conventional building was £75,900 (€96,393).

This gives a theoretical payback time of 18 years. But the actual payback is likely to be much sooner, as home buyers are clearly prepared to pay a premium to live in this kind of building.