A hidden challenge for renewable energy, in terms of carbon reductions at least, is making sure your cure is not more damaging than your disease. Many types of renewable power plants, for example, contain large amounts of concrete and cement, the production of which involves significant greenhouse gas emissions.
The emissions involved in construction, from concrete or other sources, seem rarely to be included in calculations of the environmental benefit arising from renewable energy. Yet it is not inconceivable that a wasteful enough construction process might produce more carbon emissions than a project could save over its operating lifespan.
A conundrum of this kind has already emerged in the energy storage industry.
Stanford’s energy storage study
Research at Stanford University has revealed that the energy input required to produce many types of batteries is almost as much as the batteries will be able to store over their lifetime. Of course, energy input does not equate to emissions, but the basic challenge, that the cost of production outweighs the benefit of operation, is similar. And it is not just construction that can generate carbon emissions.
Many of the offshore renewable energy sources currently under development, such as the wind and tidal plants taking shape off the coasts of Europe, are heavily dependent on port facilities, for example. Yet these in turn produce plenty of greenhouse gases.
According to research in 2004 by the US Natural Resources Defense Council, the average daily greenhouse gas output from a busy port is greater than that produced by half a million vehicles.
Auxiliary power for docked ships
Between a third and a half of this amount comes from the diesel engines used to provide docked ships with auxiliary power. But the US Sandia National Laboratories research centre in Livermore, California, reckons it may have found a way to deal with the problem… using our old friend energy storage.
In particular, researcher Joe Pratt thinks hydrogen fuel cells could play a part in helping to reduce port-based carbon emissions. His proposal is to mount hydrogen-fuelled proton exchange membrane fuel cells on floating barges, with each barge housing two 40-foot fuel cell containers and two similar-sized hydrogen storage tanks.
The arrangement could power a container ship with 1.4MW for two days, he calculates. Smaller vessels, such as tug boats, could make do with a single fuel cell and hydrogen container setup.
Hydrogen fuel cells in ports
Hydrogen fuel cells are already being increasingly deployed in a range of plant and equipment commonly seen in and around ports, including mobile lighting systems, forklift trucks and backup power systems. And the technology is gaining in efficiency.
In May, a group comprising Intelligent Energy, Dyson Technology, Ricardo, TRW Conekt, DHL and the UK Technology Strategy Board unveiled a design that delivers an improvement of more than 30% on the power density of previous systems.
Pratt sees hydrogen fuel cells as becoming an alternative to both diesel plants and ‘cold-ironing’, which is where vessels are connected to shore-based electricity supplies. Sandia’s research shows US port-based cold-ironing facilities are limited, but growing as port authorities try to reduce emissions in environmentally conscious states such as California.
Nevertheless, installing the necessary infrastructure is complex and can cost upwards of USD$5m per berth. Sandia says an 11-berth cold-ironing project at the Port of Oakland is costing $70m. Furthermore, depending on the nature of the grid power used, cold-ironing might not even reduce emissions that much.
Hydrogen fuel cell barges, on the other hand, use a carbon-free energy source and have the added advantage of being mobile, so they can be moved to wherever there is an auxiliary power need. Price-wise, Pratt believes hydrogen fuel cells are competitive with maritime fuels, based on hydrogen’s current cost of around $4 per kilo.
Elevating the price of hydrogen to $5 per kilo would still give an annual five-figure saving compared to combustion engines, when the lack of efficiency of the latter is taken into account.
A role in other renewable energy areas?
And if fuel-cell barges can help power ports, could they not also have a role in other areas of renewable energy plant construction and operations? The prime argument for using hydrogen might be to cut down carbon emissions, but as Sandia’s numbers show, there could also be a financial incentive for looking at the use of energy storage across the renewable power industry.
In a press note, Pratt observed: “Hydrogen fuel cell auxiliary power has the opportunity for greater impact elsewhere. While this was an unexpected finding, we discovered other locations and applications for hydrogen fuel cell power.”
The trick now will be for project developers to bear the potential of this and other forms of energy storage in mind when looking at new developments. For some, an open mind regarding energy storage might not only benefit the planet, but could also flatter the project balance sheet.
Written by Jason Deign
A version of this article was previously published in Marine Renewable Energy.