Ideas about the environmental friendliness of small hydropower plants are slowly coming to an end. The number of studies and research suggests that the harm from them is larger than the benefit is growing. The last one was published in January this year and was conducted by scientists from NOVA University in Lisbon, Portugal. The research aimed to calculate the impact of small hydropower plants and their importance as electricity suppliers within the European part of the Mediterranean.
Small hydropower plants (SHPs) are defined as "small" because they have 10 MW or less capacity. Because they do not require dams, in previous years, they were considered to possess a less negative impact on rivers and ecosystems than large HPPs. But with a growing number of such power plants across the Balkans and the European part of the Mediterranean, they're proving to be way more harmful than previously thought. Certainly, it will be argued that the matter lies within the greedy number of SHPPs built and planned, which is a political problem. Still, the study shows just the opposite: that the share of SHPPs in total energy production is little and without the real potential for growth given the global climate change that's already happening within the Mediterranean. In other words, the hyperinflation of SHPPs cannot increase the amount of electricity produced compared to the environmental damage it would do. Moreover, economic calculations show a similar result.
The study is predicated on a pre-existing list of current and projected SHPPs. For every site, the theoretical hydropower potential was calculated based on climatological, hydrological, and altitude data and the criteria for planning SHPP plants. Results for 14 countries in two different modeling scenarios (built: 4177 SHPPs and planned: 9925) were compared for the first time with national gross electricity consumption and primary energy consumption. The estimated potential was then compared with the particular data on SHPPs.
Also, the study concluded that the efficiency factor was overestimated and that existing projects have more than three times lower average productivity than the theoretical potential. The figures are even more devastating if we consider global warming scenarios that predict long periods without precipitation within the Mediterranean and shorter ones with abundant precipitation. However, because of low power, SHPPs cannot utilize excess water in heavy rainfall, so their efficiency remains low again.
In short, the study concludes that the potential (overestimated) contribution to the energy mix of existing SHPPs within the European Mediterranean is simply about 2.6 percent of gross electricity consumption and 0.47 percent of primary energy consumption. The calculated contribution is about 3.5 percent lower and falls to about 0.74 percent of gross electricity consumption and 0.12 percent of primary energy consumption. Furthermore, with the construction of 5,748 new plants and doubling the number of SHPs, their potential (overestimated) energy contribution is growing from 2.6 percent to 4.4 percent of gross electricity consumption and from 0.47 percent 0.79 percent of primary energy consumption. Electricity production in SHPPs largely depends on the environmental condition and might vary by over 50 percent of annual production years with favorable and non-favorable conditions. Results vary by region because drought in one region usually means high productivity in another. SHPPs have a better and more stable potential in mountainous areas (due to the combined effect of height and rain caused by the form of the terrain). Therefore, the Balkans have greater hydro potentials than Greece, Spain, France, and Italy.
However, even the Balkans aren't safe from temperature change. Moreover, in recent years, the Balkans have been under the threat of both floods and droughts happening in the same year, during a scenario of worldwide warming averaging 2 degrees Celsius per annum (although we are In the scenario of global warming at an average of 2 degrees Celsius per year (although we are currently warming to three average degrees), the flow of streams and rivers is predicted to fall by 10 to 30 percent. And with droughts and water shortages, the potential of hydropower plants will decrease even more. High levels of precipitation followed by long droughts will mean an even greater decline in electricity production from hydropower, as water scarcity would encourage greater competition for water. The priority would be the supply of water for human consumption, ecosystems, and agriculture. Consequently, most of the flow will exceed the turbine's capacity and will not be used for energy production. Long periods of low flow will produce small amounts of electricity.
These two combined effects will greatly reduce the production of Mediterranean hydropower and make SHPPs unusable. Exceptions are locations where network connectivity is greater than the effects of installing SHPPs in ubiquitous systems such as irrigation, water supply, or wastewater systems. The latter are mostly located in areas where environmental damage has already been done.
Furthermore, the value of electricity from SHPPs ranges from 40 to 300 MWh, which is very expensive, since the wholesale market value of electricity in Europe is from 40 to 60 euros per MWh, and this is all without the cost of investing in energy efficiency and without leveling the price of competing emerging technologies (such as advances in photovoltaic cells). Mini hydropower plants have therefore used up their purpose, both economically and environmentally, and why they're still being forced continues to be only a political issue.