Assessing environmental impacts of renewable power

Kapitel i bok, 2014

Electrical power systems based on renewable energy sources are often intuitively perceived as environmentally benign. This may be true at least for comparisons between electricity generated by combustion of fossil fuels and non-combustionbased renewable sources, at least in terms of contributions to greenhouse gas (GHG) emissions (Chapter 7) and other air polluting gases. However, there exists no system generating electric power for applications on commercially relevant scales that is completely without unwanted environmental side effects; it is more a question of which environmental effects and their severity. Given the serious implications of climate change, the motivation to find substitutes for fossil-based energy systems is strong, but it is likewise important to not solve one environmental problem by creating another, although of a different type. In order to prevent that, systematic investigations and assessments of the environmental performance of different renewable electricity sources become crucially important. The methods applied for environmental assessments of renewable energy sources need to be applicable to a number of fundamentally different energy systems, spanning from the construction of offshore wind power farms to hydroelectric power dams. These different energy sources provide a set of very different environmental impacts occurring in many different ecosystems. The challenge of the environmental assessment methods is to deliver assessment results that are fair and encompass the various significant environmental impacts under different conditions. Particularly when seen from a life-cycle perspective, encompassing the raw material extraction, production and use of the energy, a number of environmental impacts in terms of both resource extraction and emissions become apparent, even for renewable energy systems. Therefore, careful consideration of environmental impacts of renewable energy systems along the entire life-cycle of the energy systems is important to avoid serious environmental repercussions (see also Chapter 8). In addition, based on earlier experiences, it is apparent that the specific design, location and scale of e.g. hydro and wind power installations are factors that to a large extent determine their environmental impacts (see also Chapter 9). A smaller installation will often result in less environmental impact than a large-scale. These factors are so-called site-dependent and cannot easily be assessed in a standardised manner, which calls for flexible and adjustable assessment methods that can be adapted to the specific case. An unfortunate location of a hydropower dam does not mean that the entire technology carry unacceptable environmental impacts, just that the specific location or design in the specific case is unfortunate. This chapter aims at a general description of the challenges posed when trying to assess environmental impacts of renewable energy technologies and to, with limited technical detail, introduce the ways environmental impacts are assessed. Furthermore, a few specific examples will be employed to exemplify environmental impacts of renewable power systems.