Environmental Assessment

 

  • greenhouse gas emissions

The most urgent environmental concern on a short term remains the reduction of green house gas emissions. The computing of greenhouse gas emissions associated with fossil fuels and other energy sources, or the respective variation associated to energy saving measures, is well known and a well established standard.

 

Some special attention may be paid, nevertheless, to what is the „right“ emission factor to be applied, both for external energy supply in general and specially for the electricity grid:

 

- Average vs. marginal values: from the point of view of a single project with a small energy demand with respect to the grid as a whole it can be supposed that the grid is reacting in a „differential“ or marginal way to (changes in) electricity consumption. Not all power plants will react in a proportional way to changes of consumption of one consumer (as would be suggested by applying average values), but very probably only the „last one“ in the supply cascade will modulate it’s output. Therefore, marginal coefficients will give a more reliable estimate of the real impact of variations in demand.

 

- Time (yearly) averages vs. instantaneous values: the generation mix, and which type of energy source or power plant is the decisive last one depends strongly on time. E.g. in times of excess generation of renewable electricity (specially wind and PV) may even be for „free“ in terms of greenhouse gas emissions, whereas in times of valleys of renewable generation and high demand fossil fuel based plants with correspondingly high greenhouse gas coefficients may be the dominant ones.

 

A reliable estimate of the real impact of energy consumption or energy savings on GHG emissions therefore requires a time-dependent analysis of energy consumption and the application of time-dependent GHG-coefficients.

 

Time dependent GHG coefficients, nevertheless, will not always be easily available. A workaround may be provided by approximate models based on more easily available data such as weather data (as a proxy for wind and PV availability), daytime, weekday, and day-of-the-year in order to account for daily, weekly and seasonal variations of demand, and so on.

 

Local, regional, national, supra-national ? The right (in the sense of: best reflecting the real impact) „electricity mix“ to be applied will depend on the real interconnectivity of the electricity grid on all these levels. Obtaining information on this may be difficult, and availability of data may be a limiting factor for addressing this question.

 

 

  • environmental and comparitative assessment of renewable energy sources and technologies

The necessary large scale deployment of RES also has an important environmental impact. Some of the most obvious items in this context are:

 

    • land use (e.g. on-shore wind parks, large ground based PV, energy crops, ...) may lead to a competition with other uses (agriculture), strong visual impacts on landscape (e.g. wind parks on hills in natural parks, high voltage transmission lines, etc.).

    • use of raw materials (lithium, copper, rare earths, etc.) and associated social and environmental impact due to mining.

In many regions social movements are already forming against RES, which are not willing to accept the story that there is no other choice but between the big evil (fossil fuels further pushing climate change) and another, even if comparatively smaller one (huge RES projects).

 

Another important aspect is the limited (local) availability of some of ther RES:

    • local biomass resources (e.g. residual wood chips generated by a sustainable local forestry) are limited.

    • available surfaces with low environmental impact for solar energy use (PV or solar thermal; e.g. roof surfaces on buildings or already otherwise sealed surfaces, such as parkings; ground with little or no competing uses, such as ground areas along motorways, etc.) are limited.

As these are scarce resources, they are not completly for free. Using limited resources for one purpose means that they cannot be used for another, and in consequence they should be used there, where their impact is biggest. E.g. limited local biomass resources should mostly be used in periods where the availability of other renewable sources is small (e.g. for heating in periods with little availability of wind and PV).

Due to the above mentioned, demand reduction and an assessment of the impact of RES use and it’s minimisation is required also for a mid-term scenario (hopefully arriving soon) where all energy sources will be renewable (with zero GHG emissions) and the technology choices necessary for this purpose.

 

Sketch of a methodology for quantitative comparison of different RES systems:

 

It surely will be neither possible nor desirable to assess all these complex issues by one quantitative parameter equivalent to CO2-equivalents in assessing climate impact. Many of these issues will have to be solved by political discussion and negotiation.

 

On the other hand, in spite of the complexity in general terms one can state that the environmental impact is strongly correlated with the size. Therefore, the use of some quantitative indicator for environmental impact, such as a RES-use-footprint (which could be measured in m2 of land use, kWp equivalent of ground based PV, or whatever). Implementation of such a measure then would require establishing some conversion factors (by convention) such as

- how much footprints is a kWp of PV, and how much a kWp of wind

- how to correct depending on the specific properties of each application (e.g. a single wind turbine vs. the same turbine within a large wind park, etc.).

 

For practical purposes, assessing the RES use in a specific project and it’s potential impact some qualitative observations and reflections can be made:

 

  • consumption of renewable energy in periods of excess availability will have little or zero impact. The same is valid in the opposite sense for local renewable energy generation

  • in periods of high demand and low RES availability, where the existing RES supply is already at it’s limit or even non-renewable sources (fossil fuels) have to be used, each kW of additional demand will 1:1 translate into the requirement of 1 kW of additional installed capacity.

  • in what refers to the requirement of additional installed capacity (for covering additional demand) the decisive parameter is not the average or the sum over the year, but the worst-case period, i.e. the one with the highest additional demand for installed capacity.

 

  • nuclear energy and nuclear waste

Furthermore, nuclear energy, in spite of having (almost) zero GHG emissions, in our opinion has no place in a future path to a sustainable energy supply. The argument in first place is not even the high associated risks (Tschernobyl, Fukushima), but still more the non-resolvable problem of keeping nuclear waste securely separated from the biosphere during several centuries. Charging several dozens of generations of mankind in the future with the duty of having to handle and to supervise the waste generated in two generations today is by orders of magnitude far beyond any reasonable and responsible economic, social and environmental consideration.

 

- a methodology for correcting GHG emission data in scenarios where nuclear energy is still part of the energy-mix will have to be applied in order to take this aspect into consideration.