Prelude to the Dyson Sphere… did anyone mention space-based solar power?
Space-based solar power (or “SBSP”) involves the deployment of solar sails (very large solar panels fixed to a satellite) in space to capture and generate solar energy, and then transmit such energy to receivers on Earth. While this may sound like science-fiction, there are good reasons why we should be paying attention.
First, climate change is one of mankind’s greatest challenges. Governments are just waking up to popular calls to radically rethink energy generation and consumption. SBSP may be a necessity if we are to achieve the stretching climate goals that are currently being signed up to – net zero by 2050 for the US, EU, Japan and South Korea and by 2060 for China. These are challenging targets and it is likely that innovative approaches will be needed to achieve them. This helps to explain why SBSP is drawing increased attention from scientists and governments worldwide.
The UK Government has recently commissioned a study into the feasibility of SBSP, which will consider the engineering and economics of such a system. In May 2020 the US Naval Research Laboratory launched a solar tile module to test the viability of converting sunlight into microwave energy outside of the Earth’s atmosphere. Meanwhile, Chinese researchers have been studying the effect of microwaves beamed back to Earth on living organisms, and the Chinese government has set a target to deploy a 100KW SBSP station in low-Earth orbit by 2025, and a 1MW station by 2035.
Second, this space-age technology may have an edge over other clean energy sources. It should capture solar energy more efficiently than Earth-based solar farms, as it does not have to deal with sun light being absorbed by the Earth’s atmosphere. Moreover, SBSP is not troubled by the intermittent generation issues suffered by wind, hydro, or (planetary) solar panels – it can capture solar energy around the clock. Consequently, SBSP deployed at scale could help to achieve our climate goals by:
- generating efficient, affordable and clean energy;
- alleviating our reliance on ‘firming’ infrastructure (battery storage, pumped hydro-storage, or hydrogen storage) by providing a constant supply of energy; and
- reducing (or even removing) our need for carbon capture as we move away from requiring dispatchable (dirty) energy.
How does it work?
The current concept involves the use of solar panels attached to satellites to collect solar energy. This energy is then converted into high-frequency radio waves that are beamed back to ground-based receivers connected to the electrical power grid. There are two types of satellites: large microwave-transmitting satellites that transmit huge quantities of energy to the ground-based receivers, and smaller laser-transmitting satellites that transmit much smaller amounts of energy. Whilst both are judged to have potential, there is currently greater emphasis on the former.
Of course, there are a number of challenges to be overcome before this technology becomes anything more than a work of science-fiction.
Firstly, haulage. Launch vehicles (including reusable launch systems, along the lines of those being developed by SpaceX) will need to become cheaper to make the economics stack up. While launch costs have plummeted in recent years, further reductions in the price-tag will be necessary before SBSP becomes viable. In addition, technological advances will be necessary to considerably reduce the size and weight of the SBSP system itself.
Secondly, advances will be needed to in-orbit construction and maintenance. Thought is already being given to this: the California Institute of Technology has proposed using a modular design, consisting of thousands of ultralight solar cell tiles; whilst the University of Liverpool is exploring new manufacturing techniques involving 3D printing to print ultralight solar cells onto solar sails to create large, fuel-free power stations in space.
Thirdly, there is the issue of getting the power, once collected, safely and efficiently back to Earth and into the power grid. Currently there is likely to be too much energy loss along the way. However, researchers are considering options – for example, the Japan Aerospace Exploration Agency has developed designs and demonstrated an orbiter system that should be able to covert the electricity from the solar cells into energy waves and transfer them to an antenna on Earth to then be converted back into electricity.
A New Hope
SBSP is in the origination stage and there are a number of technical hurdles to overcome. Alongside these, a supporting legal and regulatory framework will need to be developed, alongside a sufficiently broad and deep insurance market to withstand losses when things go wrong. But watch this space: it may not be too long before we have a proof of concept, before SBSP starts to write itself into the pages of science-fact rather than science-fiction.
 For the joint-press release by the UK Space Agency and the Department for Business, Energy & Industrial Strategy, see here.