Renewable Energy

Renewable energy (RE) technologies have a major role to play in our energy future due to the earth's limited supplies of fossil fuels and to help mitigate the effects of the global warming. Renewable energy research has been increasingly important since the signing of the Kyoto Protocol, and both solar and wind industries are growing rapidly. RE research at Heriot-Watt University focuses on five main areas:

1. Photovoltaics and solar energy;
2. Renewable energy systems;
3. Minimising CO2 emissions;
4. Biofuels;
5. Wind and Marine Energy

Our RE research plays a key role in the Joint Research Institute (JRI) in Energy, a joint initiative with the Institute of Energy Systems at the University of Edinburgh. This represents one of six research institutes that are part of an exciting, vibrant, research venture in engineering and mathematics, created as a result of £22m of investment from OSI and SFC. (Richards, Mallick, Wilson)

Photovoltaic (PV) modules convert sunlight directly into DC electricity. The two main challenges for PV research are: i) to reduce the amount of silicon used to make a PV module, and ii) to increase the conversion efficiency of PV modules. Achieving either or both of these goals will result in a reduction in the cost of the PV module (£/W) and solar electricity (£/kWh). PV research at Heriot-Watt focuses on five main areas:

High efficiency silicon solar cells: enhancing the efficiency of Si PV devices via improved surface passivation based on amorphous silicon (a-Si) thin films and its alloys.

Luminescent down-shifting (LDS): luminescent materials are placed in a layer to absorb short wavelength (UV-blue) light - a region where many commercially-produced PV modules exhibit a poor spectral response - and re-emit this light at longer wavelengths, where the solar cell exhibits a very good spectral response, thus enhancing the conversion efficiency. Luminescent solar concentrators (LSC): relies of luminescent materials contained within large area polymer sheets to act as a collector. Luminescence is then converted to electricity via solar cells being mounted on the edge of the LSC sheet, thus forming a solar concentrator that can concentrate diffuse light, requires no solar tracking, and is well suited to building integrated photovoltaics (BIPV).

Concentrating Photvoltaics (CPV): optical and thermal design, simulation and fabrication of compound parabolic concentrator (CPC) elements for concentrating sunlight in the range 2 – 10X, modelling of high concentrating (in the range of 100 X) point focus Fresnel based CPV for power generation. Low concentrating CPCs are also designed for BIPV applications and suitable for Northern European climatic conditions.

Flexible thin-film solar cells: the main research challenge in this area is to fabricate a-Si:H solar cells on textile substrates for application in smart clothing.

Renewable Energy Systems (Peacock, Richards, Mallick, Früh)

There are currently three strands of RE system research. Firstly, we are developing RE powered desalination (membrane filtration) systems, specifically for application in developing countries and disaster relief areas. This is a collaborative together with Environmental Engineering at the University of Edinburgh. Research at Heriot-Watt is primarily directed at understanding the response of such directly-coupled systems to energy fluctuations when no electrical storage is present. Secondly, we recently received external funding for the development of an outdoor RE test-site at Heriot-Watt This will be comprised of two PV arrays and an array of small wind turbines. Thirdly, we are investigating alternative energy storage devices to batteries, including banks of supercapacitors for short-term storage as well as an electrolyser - hydrogen fuel cell combination together with a concentrating PV system.

Minimising CO2 emissions (Peacock, Newborough, Chen)

Our research towards minimising GHG emissions (such as CO2) has approaches. Firstly, in the built environment, the following approaches are being investigated in a range of buildings to determine their effect on the economic and environmental system performance:

• The effect of micro-generation on UK domestic sector load profiles;
• Carbon dioxide (CO2) savings attributable to micro-generation systems;
• Energy systems analysis – micro-generation, hydrogen production and hybrid vehicles;
• Time variant carbon intensity of network electricity;
• Assessment of technologies for reducing CO2 emissions in built environment;
• Research, product development and building application of dynamic insulation technology

Secondly, we perform modelling (and collaborate with international partners for experimental verification) of the accurate prediction of storage efficiency, safety, and cost of proposed sequestration technologies, including our oceans.

Biofuels (Chen)

Biofuels research activity is the investigation on mechanisms of biofuel spray, auto-ignition, and combustion by means of laser-based technologies and computational fluid simulations. The objectives of this work are to find out the mechanisms of the low carbon & efficiency combustions, developing sub-models of auto-ignition and emissions of bio-fuels, and applying the developed technologies to the engineering.

Wind and Marine Energy (Früh, Peacock, Richards)

Wind energy as a renewable resource is now well-established but challenges remain for the assessment of the interaction of the turbines with the wind their implications for the performance of turbines, especially for small turbines. Microwind installations are a contentious, yet integral part of domestic or small-scale energy systems. Research here focusses on studies of performance assessment and prediction of small wind turbines in urban, sub-urban or rural environments, using numerical studies and field studies, the latter involving renewable energy test sites at Heriot-Watt University and the University of Edinburgh. The modelling, using advanced Computational Fluid Dynamics (CFD), aims to predict the energy output from a wind turbine installed in a realistic domain and provide some guidance for optimum turbine placement.

Closely linked to the modelling of power generation from wind turbines is the power generation from a marine current. Both, the power output from a turbine in a tidal current, and its effect on the downstream environment and other turbines is being assessed using CFD.