Social scientist (bursts in the room excitedly): Hey, there’s a new research grant available to study what happens when people start making their own energy. We should put in a proposal.
Physical scientist: Whoa there. You’re talking nonsense. People don’t make energy. This may seem to be nit-picking but you have to get this right. One of the fundamental physical laws is that energy is neither created nor destroyed − it can only be transformed from one form of energy to another.1 You could use the word ‘generate’, but not ‘make’.
Social scientist: OK, I’ll try again. The research call is about people generating energy from solar.
Physical scientist: What kind of transformation are you talking about? A photovoltaic (PV) panel captures light energy from the sun and transforms it into electrical energy. A solar water heater captures heat energy from the sun and transfers this heat into the water. Which one did you mean?
Social scientist: Oh, I meant PV, people generating energy with PV.
Physical scientist: To be really accurate, it is generating electricity using PV. This is another bugbear of mine. People often say energy when they mean electricity, but you can get yourself into trouble that way. I’ve heard lay people saying that New Zealand is doing pretty well because 80% of its energy is renewable … but that’s wrong. Around 80% of the electricity is generated from renewable sources, but if you look at our primary energy supply it is more like 40% renewable [5].
Social scientist: When you say primary energy, what do you mean?
Physical scientist: Well, there are different ways you can put figures on energy, and some are more useful in some circumstances, and some in others. If you’re interested in how much energy is used by the people and businesses in your country, then primary energy is a useful concept. It refers to the raw energy that goes into the system before it has been transformed by human-derived processes into other forms of energy. Primary energy includes coal, gas, geothermal heat, hydro, wind and sunlight. Some of this will be used directly, such as burning coal for industrial heating, and some will be transformed into other forms of energy that will subsequently be used to do work, such as burning coal to generate electricity. Primary energy is usually measured in units of joules, with a metric prefix (a kilojoule is a thousand joules, a megajoule is a million joules, and so on). To measure large quantities of energy the International Energy Agency and countries that use imperial units typically use Tons of Oil Equivalent (TOE) as the unit. This is the energy released as heat by burning a tonne of crude oil, which is approximately 41.9 thousand-million joules (gigajoules).
Social scientist: Why is primary energy measured in joules and my power bill in kilowatt-hours?
Physical scientist: It’s another convention. Household electricity use is normally measured in kilowatt-hours, where 1 kilowatt-hour is 3.6 kilojoules.
Social scientist: I’ve never really understood the difference between kilowatts and kilowatt-hours.
Physical scientist: It’s the difference between power and energy. Physicists and engineers grit their teeth when people use ‘power’ and ‘energy’ as if they mean the same thing. Power is how much energy your appliance or your house draws each second. If you are using 9000 Joules per second, the power is 9 kilowatts. Energy is how much has been used to accomplish something over a period of time, like boil the kettle, and for electricity that’s measured in kilowatt-hours. Think about it like a hose with running water. Power is akin to how much water comes from the hose each second and energy is akin to the total amount of water that has come from the hose to do some task, like filling a tub.
Social scientist: OK, got that. But let’s get back to this research proposal. Are you keen? I think it’s a really great topic, and PV has amazing potential to replace all of that non-renewable energy we use.
Physical scientist: I’m keen, but I don’t agree with you about PV-generated electricity being able to simply replace other forms of energy. There are a few physical problems. One of them is that the sun isn’t in the sky all the time, so you’re only generating for part of each day, and that varies with latitude and weather patterns and time of year. Another problem is that the times when people use most power is in the morning and evening, while the maximum irradiation is in the middle of the day. Storing surplus electricity in batteries isn’t yet cost-effective in most places, so most grid-connected households end up feeding power back into the grid at the same time. This can lead to issues for network companies in managing the impacts of the power surges on the system. And the energy sector still has to be able to generate and supply as much electricity to the households as if they didn’t have PV, to account for times that PV isn’t generating, so it’s not necessarily any cheaper to run the system.
Social scientist: But can’t we use the electricity from PV to replace fossil fuels?
Physical scientist: In some situations this makes a whole lot of sense, such as using it for electric vehicles, which can be plugged in at home and are really efficient. But for other uses such industrial heating, it might be much less cost-effective and efficient than using fossil fuels, at least at this point of technological progress.
Social scientist: What do you mean by efficient?
Physical scientist: When physical scientists talk about energy efficiency they usually mean using less energy to do the same amount of work, or to provide the same service. For example, an incandescent light bulb is energy inefficient because only about 2% of the electricity going into the bulb is transformed into light energy. In comparison, compact fluorescent lights are more energy efficient at about 10%. You can also talk about the efficiency of energy generation. Most PV modules transform between 12% and 25% of the light energy that they receive into electricity whereas wind turbines transform 30–40% and large water turbines 80–90% of the available energy into electricity. Efficiency can also be assessed in other ways such as how often the generator is working to capacity. No energy transformation that I’m aware of is 100% efficient – there is always a loss at every transformation.
Social scientist: So where does the lost energy go?
Physical scientist: We call it entropy – a quantity related to the energy that’s unavailable to do any work. Usually the lost energy becomes low-grade heat, like the warmth you feel from incandescent light bulbs or from your TV, which dissipates into the environment. A portion of electricity is also lost as heat when it travels along power lines.
Social scientist: You keep talking about energy doing work. But not all energy is used by people to make things happen for them.
Physical scientist: Of course not! Energy is embedded in everything around us. It is the fundamental phenomenon that created the universe, along with gravity. Our life is only possible because plants capture energy from the sun, and we eat the plants, or eat the creatures that eat the plants. But when physical scientists in this field talk about energy they don’t usually include all the energetic processes in the planet – they draw a boundary around the energy that humans harness to get work done.
Social scientist: Energy is so integral to human enterprise and wellbeing, I don’t know why more social scientists don’t take an interest in it. For a start, the industrial revolution was powered by coal, oil and gas, which originally came from sunlight captured 300 million years ago. Today’s global economy is reliant on vast energy inputs, and around 80% of that is still fossil fuel [6]. There are so many issues that need social research. The carbon dioxide released from burning fossil fuels is the major cause of climate change, so how can the world rapidly reduce energy-related emissions? How should we address issues of inequality of access to energy, resolve environmental degradation, reduce geopolitical tensions around access to energy resources, and defuse the vested interests in maintaining high levels of use of fossil fuels? Did you know that 6 of the 10 biggest companies in the world are energy companies based on the use of fossil fuels, and another two are car companies? [7].
Physical scientist: I didn’t know that, and it suggests it’s going to be really hard to make the change to a renewable energy economy. What I do know is that there are already many technological solutions that would enable the world to use energy a whole lot more efficiently, and to switch to renewable energy for most processes, but we physical scientists don’t know how to make it happen. It’s a social and political problem. Your territory.
Social scientist: Its shared territory. Given the world needs to make substantial emissions reductions over the next few decades and get close to net-zero carbon by the second half of the century to keep within the 2° limit [8], it is going to require major changes in all systems of production and consumption. Some social scientists call this a socio-technical transition – a change that involves both technologies and behaviours at all scales, from individuals to corporations and governments [9,10,in press]. Research on PV is especially important in this respect, as PV prices are falling rapidly and in some places it is already cost competitive with other forms of electricity generation, and new installations are occurring at record levels. Also, PV is affordable at a household scale, unlike almost every other generation type, so it could be a game-changer for distributed generation if it keeps growing.
Physical scientist: How can interdisciplinary research help?
Social scientist: It helps by bringing together different perspectives on knotty problems, and enabling the team to investigate the technical and societal angles in an integrated way. That’s why I’m interested in this research opportunity on people taking up PV, because it’s likely to involve prior and subsequent changes in attitudes and behaviours at a household level, and I’m keen to know what these are. For example, do people use more or less electricity? Do they shift activities to different times of the day? Do they become more energy literate? Do they become more conscious of the efficiency of their appliances? Does it make them more likely to want to buy an electric vehicle or batteries for storage?
Physical scientist: And I’d like to measure things like how much electricity they generate from the PV, how much self-consumption they achieve, and how their patterns of consumption change. Also, do they switch to using more electricity and less of other fuels?
Social scientist: Also, it might lead to households collectively playing quite a different role in energy systems than they have previously, given that they would now be producers as well as consumers of energy. I’m interested in whether people become more willing to share or gift their surplus energy, and in the possible emergence of local energy markets. We’ve already done some preliminary thinking about how PV uptake could lead to both behavioural change at a household level, and changes to traditional systems of energy supply [11]).
Physical scientist: It would be good to do our research at a location where there was a lot of new PV going in to an area, so we could measure the changes in power flows on the grid, and the effects of this on power quality, and find out how much less energy is lost to entropy given it isn’t having to travel so far to be used.
Social scientist: If we’re going to work together on this, we need to have a common framework that supports the integration of your physical data and my social data.
Physical scientist: I agree. Any ideas?
Social scientist: I suggest we use the energy cultures framework. By ‘energy culture’ we mean the particular combination of energy-related material assets, behaviours and norms that our research subject has, and how the interactions between these result in different amounts and patterns of energy use. If we want to understand a household’s energy culture we need to look at the things that they have (e.g. types of heating devices and insulation), what they do (e.g. daily routines, thermostat settings) and how they think (e.g. expectations of warmth and comfort), and how these interact, and how they change over time. All of these things are measurable, some using physical units, and some using social science measures. Some colleagues who are interested in the evaluation of energy interventions are developing a social science measurement framework based on the energy cultures concept using validated scales so we might build on that [12], [13]. And we can also track how households’ aspirations change over time, such as their interest in gifting or selling surplus energy locally rather than selling it back to energy companies.
Physical scientist: I’d like to have good data on the households’ energy use prior to their adopting PV, so ideally we should set up a monitoring system first, down to appliance level if possible. And maybe some time-use surveys to see what they’re actually doing.
Social scientist: And we could work with the electricity distribution company to understand what power flows are going on at the local network level, and whether they see benefits to network management if local energy markets emerge. That way we can start to look at the potential for PV uptake to drive a socio-technical transition, even at a small scale.
Physical scientist: Sounds good. Let’s start to design this research proposal ….
Stephenson, J. (2017). What does energy mean? An interdisciplinary conversation. Energy Research & Social Science, 26, 103–106. https://doi.org/10.1016/j.erss.2017.01.014