Centre For Alternative Technology (CAT)

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Wind & Sun design & install Minigrid Backup system for WISE project at Centre For Alternative Technology, Machynlleth, Wales

Mini –grid system for Europe's leading eco-centre. It is staffed by 90 permanent staff and volunteers all year round, with a further 60 people during the summer months and receives around 65,000 visitors every year.

Along with a range of interactive displays, there are working examples of environmentally responsible buildings, renewable energy generation, sustainability in the home, organicgrowing, composting and waste management, each demonstrating what can be done to reduce our impact on the planet.


View the CAT site map here

Designed for low energy consumption in use, electricity contributions come from on-site renewable energy sources including solar photovoltaic panels, hydro and wind turbines.WISE also hosts an impressive array of solar thermal collectors which contribute to the domestic hot water needs.

Designed to be highly energy-efficient in use and in construction, WISE incorporates a range of low-embodied-energy materials, such as hemp and lime, rammed earth, and sustainable timber. 

This is a 30kW Sunny Backup System using:

  • 6 x SBU-5000 Sunny Backup inverters;
  • Automatic switch box AS-Box-XL;
  • Hoppecke Batteries giving 2 x 57kWh storage;
  • Hydro turbine & Wind turbine connected using Windy Boy inverters;
  • 20kW PV, 4kW Hydro, 3.5kW Hydro and 600W Wind connected to the Minigrid

The renewable energy produced at C.A.T is fed into a battery bank and connected together through the Automatic Switch Box along with the load and the national grid. In normal operation, the renewable generators provide power to all the loads and excess power is exported to the grid.

In the event of a power failure, the CAT electricity system is isolated from national grid and the renewable generators continue to operate like as an island grid system. The Sunny Backup inverters regulate the power generation according to the demand of power ensuring continuous efficient operation of renewable generators and maintaining power to essential site loads.

The back-up battery is sized such that even if there is no wind, sun, water or biomass it will provide power for at least 3 hours. If the batteries become low power is disconnected from  less critical loads to make sure the energy is available for the WISE emergency lights, servers and telephone system.

Once the national grid is restored then the system works as normal.

The system will be used for courses and consultancy as a model for Zero carbon CAT and provides a demonstration project for small communities interested in island grid / micro grid system.

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