Parque Eólico a orillas del mar-Wind Farm at the seaside


Renewable energy can cost very little but can’t guarantee reliable output. Murdoch Mactaggart learns of a company using hydrogen to store energy and deliver it on demand, hoping to change the face of motoring.

Renewable energy supply is unpredictable. There’s no guarantee the sun will shine or winds blow when needed. Moving electricity around a national grid can help to balance supply and demand but that’s wasteful of energy, still needs boosting to meet demand spikes, and is contrary to much current thinking about localising energy generation and consumption.

What’s needed is some form of efficient energy storage, perhaps using energy to change chemical states, duly harvesting the energy on reversal. This is how batteries work but batteries still have serious limitations and current thinking is towards using elements such as hydrogen. “The holy grail of the electricity industry is low-cost, highefficiency energy storage at scale.” says Dr Graham Cooley, CEO of ITM-Power plc. “Batteries can’t do that but with electrolysis equipment you can store energy as a chemical fuel. And it’s flexible – if you need to store more then you just use bigger tanks.”

Energy security

Sheffield-based ITM Power designs and builds a range of portable hydrogen-generating units based on protonexchange membrane electrolysers but also develop technology for high-density fuel cells, particularly for vehicular use. They recently announced development of a new membrane allowing hydrogen fuel cells to deliver 2.1 watts per cm2, around three times the existing power density. This is particularly important for transport as power density determines necessary weight for a given power rating. “It’s ultimately about energy security and adding value to renewables.” adds Cooley. “Renewable energy can be very cheap to produce and you can use it to electrolyse water into hydrogen and oxygen and then use the hydrogen as a transport fuel. You don’t get any carbon footprint from the energy production or transportation and, importantly, you even out the intermittent nature of renewable energy production. So apart from decarbonising transport and reducing dependence on damaging fossil fuels you can maximise your investment in renewable energy.” Hydrogen fuel cells, according to Cooley, are around twice as efficient as internal combustion engines but fuel-cell cars are not yet widely available. They’re also expensive although Cooley claims that vehicle manufacturers expect to offer such cars at prices comparable to conventional petrol vehicles by 2015.

Transitional approach

“The future is undoubtedly the fuel-cell vehicle” he says “but ITM has just begun a year-long trial of a transitional approach, HFuel, which uses hydrogen to drive ordinary petrol-engined Transit vans. Only very minor modifications are needed and if you run out of hydrogen you just switch back to petrol. If you have air quality targets or carbon emission targets to meet you’ve got a very simple way to do that right now. Using energy from your own solar panels you can generate hydrogen and so refuel vehicles at virtually no cost once the initial capital investment has been met.” Conventional electric cars have improved hugely and can be surprisingly responsive, fast and nippy. Yet despite battery improvements they still suffer from long recharging times,
typically overnight, and a range of around a hundred miles. With a fuel-cell electric vehicle, however, refilling with hydrogen takes no longer than filling with petrol and gives a range of 400 miles or more. And with your own hydrogen
home generation unit driven by solar or wind power, fuel costs vanish instead of climbing ever higher as with petrol or diesel. Bring it on!

Fuel cells

Fuel cells are increasingly seen as powerful and flexible modern technology for providing electrical energy for a range of uses from small electronic devices through to large vehicles. Yet the basic knowledge dates from 1838 with the
first demonstration made a year later. There are several different types of fuel cell but all work in the same general way using an anode and a cathode
together with an electrolyte. A fuel is oxidised by a catalyst at the anode and separated into ions and electrons. The electrons pass through a wire to create the electric current and then recombine with the ions at the cathode. Fuel cells
can be combined in series to increase voltage or in parallel to increase current.
Various alcohols and petroleum products are widely used but hydrogen is the most common fuel. Here hydrogen is fed in at one end and combined with oxygen to give an electric current, water being the waste product. This water can itself then be electrolysed into hydrogen and oxygen for reuse and
so in a real sense a fuel cell is essentially a mechanism for storing energy chemically and subsequently delivering it in the form of electrical energy at a convenient time and location. Electrical output from fuel cells is still fairly expensive, this being principally a function of currently necessary expensive
catalysts rather than fuel costs, but against that there are very low maintenance requirements and considerable flexibility. And energy output costs are decreasing steadily as performance improves.

Publicado en: Ingenious Britain


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