ICARES: INTEGRATED COMPRESSED AIR RENEWABLE ENERGY SYSTEMS
Nottingham University, Thin Red Line Aerospace
The stated aim of the ICARES project was to find a way to make renewable energy both inexpensive and available on demand – no short order. To tackle these issues, a team from Nottingham University and Thin Red Line Aerospace developed an energy storage system that uses fabric bags of compressed air designed to be held deep underwater.
Storing compressed air deep underwater means that the hydrostatic pressure of the water provides most of the force needed to keep the pressure of the compressed air contained. It also provides an energy storage solution that can operate very close to offshore wind turbines.
Using fabric pressure vessels created by Thin Red Line – originally as a weightsaving material for the aerospace industry – the Nottingham researchers developed powerful analysis tools to determine what loads exist at various points in a fabric structure.
Alongside the innovation in this system, ICARES represents a shift in thinking about renewable energy storage. Instead of generating electricity first and then converting the energy for storage, the idea is to use wind turbines to power pumps that compress the air directly. This can then be saved to power turbo generators later on, cutting out a stage in the process and making the whole system more efficient because the energy is converted only once.
The group estimates that the concept could reduce the cost per MWh of offshore wind energy by a factor of four, avoiding added system costs associated with widespread renewable energy generation and reducing losses through repeated energy conversion.
DEVELOPMENT OF WIDELY ACCESSIBLE ORGANIC SOLAR CELL TECHNOLOGY
Warwick University, Molecular Solar, Warwick Ventures, Kurt Lesker, Asylum Research, New World Solar
First-generation solar cells are made from expensive refined silicon and while second-generation semiconductor films are manufactured at a lower cost their development is limited due to toxicity and low abundance. The idea for third-generation cells, which originated in Warwick
University’s chemistry department, is to use organic photovoltaics (OPVs) that offer the prospect of very low-cost, lightweight, flexible solar generating material.
Molecular Solar was spun out to develop this idea for commercialisation and has since formed a consortium to create marketable products from the technology using £2.1m funding from the Technology Strategy Board and the Engineering and Physical Sciences Research Council.
The cells are composed of thin films of a cheap and abundant organic semiconductor material that can harvest light from a large proportion of the solar spectrum. These are mounted on a flexible substrate developed by Molecular Solar called FLEXIFILM, and weigh less than one per cent of conventional silicon cells. The materials used can be cheaply mass produced with minimal environmental impact as they are made from
non-toxic compounds and are recyclable.
The company says its technology has the potential to reduce the cost of solar electricity generation to make it competitive with conventionally generated electricity at the point of use. This could open up a large, nonsubsidised market for photovoltaics and have a huge impact on fossil fuel consumption.
The technology also has potential for use in portable electronic devices, for example, as a solar-powered mobile phone charger that could be rolled into the size and shape of a pen, or detachable sunshades for car windscreens that powers an air-cooling unit inside the vehicle.
CRYOGENIC ENERGY STORAGE
Highview Power Storage, Scottish and Southern Energy, BOC/Linde, Leeds University
Traditional energy storage solutions have significant challenges: pumped hydro and compressed air are constrained by geography or geology, while batteries cannot yet be scaled up sufficiently and degrade over time, as well as often relying on expensive materials.
Highview Power Storage’s response was to develop a scalable system that can be built anywhere and relies on a commonly available substance. Working with Leeds University, the company designed and lab-tested a novel cryogenic energy storage system that used liquefied
air or nitrogen as the storage medium.
The technology can also simultaneously convert low-grade waste heat to electricity at high levels of efficiency. Highview says there is up to 800TWh of waste heat in the UK alone, much of it only useable for district heating or exhausted to the atmosphere.
The company has opened a pilot plant in Slough hosted by Scottish and Southern Energy adjacent to a renewable energy 80MW bio-mass plant, creating a closed cryogenic system that can store energy at times of surplus and release it when it is needed, while re-using the cold air exhaust.
Highview estimates the capital cost of cryogenic energy storage will be less than $1,000 per kW when the technology is mature, one quarter of the costs of sodiumsulphur batteries and between half and quarter of that of pumping water uphill into reservoirs. A commercial-scale 3.5MW
power generator 10 times larger than the pilot plant is due to open by the end of 2012.