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Your burning energy questions answered

 

Should governments invest in large-scale desert-based solar plants? And are manufacturers of solar and wind systems using dirty energy to produce these solutions?

In the first part of the Global Energy Prize series, Australia’s environmental scientist Barry W. Brook, answers the questions by Eco-Business readers on renewable energy.

Sophie Hughes, General Manager, CPR Sustainability, Sydney asked: As we battle with NIMBY (Not In My Backyard)-ism and planning issues, should international governments be focusing on building large scale renewable energy projects in uninhabited areas, such as central Australia or the edges of the Sahara? Is this feasible and does this mean that we need to focus more efficient infrastructure and storage capacities, rather than being dazzled by the technologies themselves.

Answer:

All energy technology options have their pros and cons, and so investment decisions should ideally be based on a set of logical, consistent and unbiased criteria. This should include considerations of cost, externalities (e.g., CO2e emissions and toxins emitted per MWh of energy), technological maturity, dispatchability, reliability, safety, energy returned on energy invested, sustainability and security of material inputs and fuel, facility lifespan, land use, public acceptability, and so on.

Typically however, many (most) of these are left out of decision making – public and private. As an example, a recent analysis of the ‘fit-for-service criteria’, life-cycle emissions and levelized costs of technology options, can be read here,and here. So, as to the specific question, it would make sense for governments to invest in large-scale desert-based solar plants if, on the basis of a rational analysis using these criteria, it was shown to be a superior option compared to alternatives. At present, desert solar has many large uncertainties, especially in terms of cost (including transmission from remote locations), amount of energy storage required, and technological maturity.

My view is that it is worth developing, via multi-lateral funding and RD&D initiatives, a number of large demonstration plants for a range of new renewable and next-generation nuclear technologies – and then on the basis of performance, governments and the market can work together on commercial deployment. For a checklist of what types of details any large-scale alternative energy plan should (ideally) cover, see here.

Another reader, Sunil Sood, posed this question: What are the “Real Energy Payback Periods” for Solar PV and Wind Energy Systems? Taking into account the energy consumed during manufacture of components, balance of systems, transportation, installation, servicing and variations in availability of energy and usage patterns, actual life expectancy.  Are we consuming more of ‘dirty coal’ to produce these so-called ‘clean’ energies?

Answer:

Calculating true energy paybacks are tough. Every energy system has initial investments of energy in the construction of the plant. It then must produce energy for a number of years until it reaches the end of its effective lifetime. Along the way, additional energy costs are incurred in the operation and maintenance of the facility, including any self-use of energy.

The energy payback period is the time it takes a facility to “pay back”  or produce an amount of energy equivalent to that invested in its start-up. A full accounting of energy payback includes not only the materials and energy that are input into the extraction (mining) and manufacturing processes, but also some pro-rata calculation for inputs into the factory that constructed the power generation facility, some estimate for human (worker) inputs, etc.

As you can imagine, it can be difficult to fully integrate all possible inputs. However, there are reasonable ballpark estimates for a range of technologies, including wind, solar PV, solar thermal and nuclear. Material inputs tells one part of the story, and some attempts are a standardized comparison are given here and here for a few technologies (wind, solar thermal, Gen III nuclear).

As a short-cut for estimate of total energy-returned-on-energy-invested (ERoEI), we can use studies that have looked at the life-cycle emissions of alternative technologies, and then calibrate these against the emissions intensity of the background economy used to produce the technology. This gives us an approximate ERoEI. Based on a range of studies, the estimates range from 180 to 11 for Gen III nuclear, 30 for wind, 11 for solar thermal and 6 for solar PV. That is, your PV panels would repay their inputs 6 times over during their lifespan, and if they lasted on your roof for 25 years then the payback time is about 4 years. If a nuclear plant had a ERoEI of 50 and operated for 40 years, its energy payback time would be 10 months.

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