The Marriott Heathrow hotel has become the first hotel in the Marriott Group to be fitted with a hybrid wind turbine and solar panel system as part of their ongoing 'Green Initiative'. As an integral part of their programme to reduce the hotel group's carbon footprint, the hybrid wind-solar system has helped them attain 'Gold' certification under the Green Tourism for London scheme.

The hybrid system runs alongside their new herb garden and is designed to power one of three Marriott signs on the front of the building. Ultimately, a further two systems will be installed to operate the 2nd and 3rd sign. Each sign uses low power LED's and draws 260W at 240V, so they needed to produce between 1.3kWh and 2.6kWh per day, depending on the time of year and the length of time the sign is illuminated each day. Producing this amount of power reliably each day, using the least amount of equipment and relying on the British climate, was the challenge that we faced. The decision to use a hybrid system was borne out of the fact that hybrids are capable of producing power 24-hours a day and, in general, when their is a good wind there is less sun, and when there is a lot of sun there is less wind.

After reviewing all the possibilities, we settled on a solution using a 600W turbine and two of our 100W high-efficiency monocrystalline solar panels. Given that the average wind speed at ground level is 10-knots (5.1m/s), the LE-600 will produce between 1.5 and 2.5kWh per day; mounted at 25m where wind speeds will be 15-25% higher should result in more than this. To supplement the wind turbine, the two 100W panels will produce additional electricity even on overcast days. In the summer months, the panels will be adding at least 1.2kWh to the power supply, although this is likely to be less in the winter (0.6 - 0.8kWh). As an added backup, the system uses 440Ah of leisure batteries, running through a 700W pure sine wave inverter from 'Merlin', so the sign can be safely operated for up to 16-hours with the panels and turbine disconnected. In the event that the sign needs to be operated from the mains, we also built in an changeover unit, which will automatically transfer the supply from the inverter to the national grid at the flick of a switch.

Equipment Used:

• 1 x Leading Edge LE-600 12V 600W wind turbine
• 2 x Cleversolar CS-100 high efficiency monocrystalline solar panels
• 4 x Numax 110Ah 12V deep-cycle batteries
• 1 x Merlin M-Power 700W puresine inverter
• 3 x Leading Edge DL300 300W diversion load charge controllers
• 1 x turbine start/stop switch
• 1 x 20A automatic mains / inverter changeover unit
• 20m twin-core 4mm solar cable