Guest Blog: npower’s Wayne Mitchell on Space Solar Energy

Power that’s out of this world Every time I read about another rocket successfully launching into space, I think about the implications for solar energy. Only this week, the Atlas […]

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By Geoff Curran

Power that’s out of this world

Every time I read about another rocket successfully launching into space, I think about the implications for solar energy. Only this week, the Atlas 5 rocket blasted off from Cape Canaveral, transporting a 15,000 pound US Navy satellite into orbit.

These satellites are often powered by solar energy. Imagine if you could expand that energy-generating capability to create a space-based solar power farm? It may sound far fetched, but there are plenty of reasons why I’m not the only person to get excited by this idea.

Potential for 8-10 times more energy

Firstly, lofting square kilometres of solar-collecting surface area into a geostationary orbit avoids many of the challenges which rob terrestrial solar power of much of its potential.

With issues such as surface contamination, airborne dust and clouds, periods of darkness and often less than ideal incidence angles no longer relevant, spaced-based systems are able to maximise their usage of the available solar energy. And, since the sun delivers a constant 1.4 kW/m2 even at this distance – earth is around 93 million miles away from its local star – that adds up to quite a lot.

In fact, it’s estimated that space-based solar systems may produce as much as 8-10 times more power than their earthbound equivalents.

Under these circumstances, space-based systems offer the tantalising prospect of low-impact renewable baseload power generation, with orbiting arrays supplying electricity at better than 99% availability and without the intermittency issue.

Space solar first developed in the Sixties

It’s perhaps no surprise then that since NASA’s Dr Peter Glaser first developed the idea in the late 1960s, there have been countless proposals and concepts for solar power farms in space. However, all of these diverse concepts have a common factor. They have remained at the conceptual stage, deemed either technically or economically unfeasible.

A key challenge includes the obvious requirement to create a large orbiting structure. That requires finding a cost-effective way to transport the necessary materials into space and then assemble and maintain them in the harsh extra-terrestrial environment.

The efficient and safe transmission of the power is another significant issue. Current research has focused on lasers or the more commonly favoured microwaves. In each case, receivers would need to be located on earth or on high altitude or orbiting platforms for subsequent despatch to the surface.

International will to overcome challenges

However, each of the key challenges – space assembly and construction, lighter and more efficient solar panels, and wireless power transmission and conversion – is benefitting from considerable R&D investment.

For example, in 2011 scientists from the Japan Aerospace Exploration Agency (JAXA) launched a joint research project with industry to develop more effective microwave power transmission systems. Indeed, Japan is perhaps leading the solar power satellite field, with plans to install an operational system by 2040.

But Europe, the USA, Russia and Japan are all reportedly looking into solar power satellite technology too.

Feasible but not yet cost effective

It’s also true that to some extent, space-based solar power is already clearly feasible. The vast majority of space vehicles use solar power for the bulk of their energy requirements. Indeed, solar photovoltaic technology was commercially pioneered by the space industry, with Bell Labs supplying PV cells for the Telstar 1 satellite launched in 1962, for example.

The technology has also evolved considerably since those early days, and today there are some sizable installations in orbit. For instance, at an altitude of around 400 km, the International Space Station fields an acre-sized solar array which generates upwards of 80 kW.

The realisation of space-based solar is inevitably getting closer then – although still decades away. And while the cost of such proposals is likely to keep them out of reach for the foreseeable future, economic feasibility, rather like all celestial bodies, is never static. So keep watching the skies.

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