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YouGen Blog

From energy importer to energy exporter - the story of The National Energy Foundation.

Posted by Sam Tonge on 17 August 2017 at 12:34 pm

YouGen is based in the National Energy Centre, which is the main office of the National Energy Foundation (NEF), an independent British charity, established to encourage the more sustainable use and generation of energy.

As you’d expect, the centre features an exciting and inspiring array of green building materials and technologies including solar photovoltaic systems, solar thermal hot water, harvested rain water (for toilet flushing) and a ground source heat pump coupled with underfloor heating to heat the building. However it’s not always been plain sailing with many of these systems needing additional care and attention and, on occasion, repairs, over recent years. Fortunately, as an organisation we’ve managed to overcome these challenges and we thought we’d share the story with our YouGen community.

The centre is split into two buildings, Phase 1 (completed in 1999) and Phase 2 (completed in 2004). Both feature a number of innovations which were quite revolutionary in their day and you can read more about the centre and the different systems on NEF’s website.

For this blog entry, I want to focus on the Phase 2 building (where YouGen is currently based) and outline a few of those issues and problems that we have encountered over the years.

So where do I start? Perhaps by listing the technologies that were installed when the building was designed and built in 2004:

  • An array of 20 Schuco solar PV panels totalling 6.8 kilowatts (kWp)
  • A Thermomax 20 evacuated tube solar thermal hot water system with dual 3KW immersion heater back up (if required)
  • Underfloor heating from a 13KW Viessmann ground source heat pump providing 95% of building heating needs
  • Rainwater recovery system used for toilet flushing with 3300 litre storage tank
  • 7.2kW biomass (pellet) stove for the 5% of the time when we need a heat boost in the building

The building also benefits from high levels of insulation throughout, natural controllable ventilation and use of daylight through externally shaded windows and a series of Sunpipes® from Monodraught.

Problems we have faced

All of the systems were designed as ‘fit and forget’ in that they didn’t need any ongoing interventions; thus freeing up staff time to concentrate on normal work for the Foundation; however we found that over time different parts of the technologies started to fail through a combination of natural wear and tear and simply by coming to the end of their expected lifetime.  Being a busy office environment as well as a charity, as different parts of the systems failed, decisions were made as to which technologies should be repaired as a matter of priority and which could afford to wait.

The over-arching priority was always to ensure the smooth operation of the Foundation; for example issues with heating resulted in a higher level of priority being given rather than the lack of harvested rain water for example.


Our solar photovoltaic (PV) system experienced problems with one of its inverters in 2011 (the components responsible for converting electricity produced from direct to alternating current). This was easily resolved by replacing the failed inverter, however five years later in 2016, a key interface component also failed; which meant that we couldn’t generate any electricity; which effectively resulted in a higher amount of electricity being used from the grid.

Alongside this, the main pump of our solar thermal hot water system failed which meant that we were reliant on the back-up immersion heaters as our sole source of hot water. Again, relatively simple to overcome, but it did mean that we were again reliant on grid- supplied electricity rather than solar energy.


Heating to the building is provided by a ground source heat pump and is interconnected by three underfloor heating loops covering both our ground floor and our mezzanine. However we couldn’t figure out why one of the rooms on the mezzanine level was colder than it should have been.  Earlier this year we had the system serviced and it was found that a couple of the valves used to control the flow of hot water to the underfloor piping had stuck, resulting in cold areas.  To fix this relatively simple problem we had all of the valves serviced and fitted with new flow adjusters as necessary.