Climate Change, Renewable Energy and Photovoltaics: How Does It All Fit Together?

Article by Leonardo Buizza, University of Oxford

March 27, 2018, 5:37 p.m.

We often hear about how climate change is causing irreversible damage to global ecosystems, how new power plants are opened across India, or about how a new technology will save the world. These stories are full of numbers, bold claims, and a lack of understanding of the bigger picture. This blog post aims to start from the biggest picture, that of global climate change, and gradually zoom in to describe where research into photovoltaics (PV) in the UK fits into this. Many people know different facts and bits of what I am about to discuss. Hopefully, this post will paint a more complete picture that connects the dots. There will be some figures and numbers; it is impossible to have a meaningful discussion without them. However, I will try and keep them easy to digest for anyone. Let’s begin.

The most well-known impact of global climate change will be seen via increases in average global temperatures over the 21st century. The Intergovernmental Panel on Climate Change (IPCC) release reports every few years, with the most recent one including Figures 1 and 2. These tell us two things. First, if we continue “business as usual” (the scenario labelled as RCP8.5 in Fig 1), with economic development driven by fossil fuel-based energy and with little climate mitigation, temperature rises will hit 4OC by the end of the century and keep rising. Second, to greatly slow or reverse temperature increases, we need net negative emissions by 2070. We need serious concerted action to become carbon-neutral as a minimum, and some magic hoovers that suck CO2 out of the atmosphere (see scenarios RCP4.5, RCP2.6 in Fig 1, and various approaches to cut emissions in Fig 2). This is something that is not grasped by the public at large, and is not mentioned by any politicians or influencers: to stay in the limits decided in Paris in 2015, we are currently relying on some “silver bullet” that will enable us to pull carbon out of the atmosphere. People are complacent as to the difficulty of carbon sequestration, and decision-makers are relying on it as a future crutch on which to base current policy. The issue is an incredibly serious one, and one that needs large-scale, global action.

Figure 1: IPCC projections for mean global temperature change. We are currently on a trajectory between RCP6.0 and RCP8.5. Source: IPCC

Figure 2: Possible emission pathways in order to limit temperature increases to less than 2 degrees, as agreed in Paris. Most require negative emissions from 2050 or 2070 onwards. Source: IPCC

What is the situation in the UK? We’re not doing too badly, by some measures. By 2017 our annual CO2 emissions had fallen by roughly 38-42% since 1990 – about halfway to our target of an 80% reduction from 1990 levels by 2050. This reduction was mandated by the Climate Change Act of 2008 via five-yearly “carbon budgets”, and we are currently on schedule to be under-budget for the third one. However, there is no room for complacency. The most recent government data and projections tell us that, taking into account the impact of current policies, as well as projected GDP and demographic growth and their influences on energy demand etc., we will be over-budget for the fourth and fifth budgets (see Fig. 3). By the end of the fifth budget we will have a reduction of 54%, as opposed to the required 57% - not quite there, but still, not bad. Further, the amounts that we are projected to be over-budget by for the fourth and fifth budgets have gone down relative to the projections made a year ago – progress. On top of this, the models do not yet take into account the impact of policies currently under development or future initiatives. Indeed, that is the take-home point – we are doing well, but more is needed. Especially because, if we look back at Fig 2, we’ll see that in order to stick to 2OC of warming we need to reduce emissions by about 100% by 2050, well beyond what our current budgets aim for. We need larger-scale, faster change.

Figure 3: DBEIS projections for the UK's emissions up to the fifth carbon budget, ending in 2032. We are on track to overshoot the fourth and fifth carbon budgets, without any major new policy initiatives. Source: DBEIS

Enter the UK’s current energy situation, notably with regards to renewables. The crucial point is that only one-third of total energy requirements are due to electricity. The other two-thirds are mainly down to transport, and heating and cooling buildings. (This is often a source of confusion: think of the feel-good headline, “Country X has generated 100% of its electricity from renewables for a whole day” – good job, but not the whole story!) The electricity can be generated using fossil fuels, nuclear or renewable sources. In 2017 Q3, 30% of electricity was provided from renewables, with 13% from wind and 5% from solar PV (see Fig. 4). However, as a percentage of installed capacity, or of total electricity generated, the progress of both wind and solar PV has been frustratingly slow over the past few years (see Fig. 4). The proportion from solar PV and wind both need to carry on increasing substantially in coming years, both here and elsewhere.

Figure 4: Percentage of total electricity-generating capacity, and percentage of generated electricity by solar PV and wind power (both on- and off-shore). Both sources vary seasonally, but out of phase with each other, so that they are complimentary. The increases in proportion of capacity and of electricity generated have been slow over the past few years. Source: DBEIS

What is required in terms of policy shifts, then? We can alter our overall demand and supply of energy. Government projections expect total energy demand to stay roughly flat up to 2035. Energy consumption for transport has stayed approximately constant since 1990 and is expected to remain so until 2035, but the proportion of fossil-fuel based transport will shift from 97% to 92%. This is not enough, and I would argue represents one of the largest opportunities: electrifying more transport, notably cars, will help a lot. So too would improving public transport by quickening the electrification of trains and buses, as well as encouraging an increase in its use, replacing, not adding to, usage of cars. Improving schemes for upgrading old housing stock to make heating and cooling more efficient, by installing better insulation and increasing uptake of heat pumps, will also help reduce demand and electrify heating and cooling. In both these cases, electrification is a double bonus: it weans us off the direct use of fossil fuels, and, if the proportion of electricity provided by renewables continues increasing, will also help de-carbonise our electricity supply.

We have been remarkably successful at eliminating coal from our energy supply, helping to cut our emissions so far, but only by replacing it with cleaner natural gas. This and other remaining fossil fuels need to be put on life support as we increase provision of nuclear and renewable electricity. The introduction of feed-in tariffs and renewables obligation certificates (ROCs) helped get things going. However, the replacement of ROCs with contracts for difference has removed some of the certainty for investors in renewables, and the last budget lacked announcements of any new subsidies up to 2025, further dampening the outlook for future renewables investments in the UK. Government projections expect that by 2032, we’ll still be generating 19% of our electricity from natural gas – too much. Again, this is the take-home point: we need to electrify as much as possible, and brutally decrease the proportion generated by fossil fuels.

Another word of warning is required: in order to provide energy using purely renewable sources on a country-wide scale, we need country-sized installations. This is true whether it is wind, solar, tidal, biofuels or anything else. Personally, I think this shows the crucial role nuclear power has to play in shifting us towards a carbon-free energy supply. In any case, however the shift occurs and whatever mix we end up with, it will require hundreds of billions of pounds of investment and continuous policy support in the UK alone. I do not say this lightly, nor do I take government spending for granted; I would argue that this can be viewed as sensible, long-term investment in critical infrastructure that would both pay itself back in the long run, and could be used to provide injections of spending into localised areas of the UK. Further, the cost of inaction is likely to outweigh the costs of this shift, especially if one considers the global scale of the problem.

Figure 5: Share of global shipments of solar PV in 2016. The global market is dominated by silicon, with most manufacture coming from China. New thin-film technologies (CIGS, CdTe) only make up 5% of the shipments. Source: NREL

Finally, where does the Centre for Doctoral Training in New and Sustainable Photovoltaics fit in? Students research a variety of new materials for PV devices, with the aim of providing cheaper and more efficient solar panels. As we can see in Fig. 5, around 95% of global PV sales use silicon as the photovoltaic material, with the other 5% mainly consisting of CdTe devices (the most successful of a new generation of “thin-film” PVs). The materials we work on, ranging from organics to CIGS to perovskites, are all options that, in due course, could either work with or replace silicon devices. As global capacity of solar PV increases, it is inevitable that we get a greater amount of specialisation and experimentation with the range of materials being used: some for large-scale industrial applications, others for highly specialised uses such as on satellites, for portable charging kits or to connect devices to the Internet of Things. Just as importantly, the training being given to CDT students will put us in a better position to play a critical role over the coming decades within the solar and energy industry more broadly, helping us to achieve a sustainable future for the UK as world-leaders in renewable energy.


I would highly recommend these if you are interested in more details:

  1. Fifth IPCC report
  2. Clear outline of the report’s implications
  3. Thorough overview of the UK’s energy landscape and outlook, published by DBEIS
  4. Most recent update on UK renewables, published by DBEIS
  5. David Mackay’s brilliant book ‘Sustainable Energy Without The Hot Air'