Small hydropower plants (installed power below 10 MW) are generally considered less impacting than larger plants, and this has stimulated their rapid spread, with a developing potential that is not exhausted yet. However, since they can cause environmental impacts, especially in case of cascade installations, there is the need to operate them in a more sustainable way, e.g. considering ecosystem needs and by developing low-impacting technologies. In this paper, an assessment was conducted to estimate how the environmental flow and the plant spatial density affect the small hydropower potential (considering run-of-river schemes, diversion type, DROR) in the European Union. The potential of DROR is 79 TWh/y under the strictest environmental constraints considered, and 1,710 TWh/y under the laxest constraints. The potential of low-impacting micro technologies (< 100 kW) was also assessed, showing that the economic potential of hydrokinetic turbines in rivers is 1.2 TWh/y, that of water wheels in old mills is 1.6 TWh/y, and the hydropower potential of water and wastewater networks is 3.1 TWh/y, at an average investment cost of 5,000 €/kW.

The study presents a cost effective electricity generation portfolio for six island states for a 20-year period (2015–2035). The underlying concept investigates whether adding sizeable power capacities of renewable energy sources (RES) options could decrease the overall costs and contribute to a more sustainable, indigenous electricity generation at the same time. Often, island states rely on fossil fuels which, apart from dependence on foreign resources, also includes an additional, significant transport cost. This is an extra motive to study the extent in which island states represent primary locations for RES technologies. For the aims of the present study an optimization model has been developed and following numerous runs the obtained results show that installing PV and battery capacities can delay-reduce the huge investments in fossil options in early periods. Thus, investment on RES can have a positive, long-term effect on the overall energy mix. This prompt development can happen without adding new subsidies but there is a need to address the existing socio-economic barriers with intelligent design of financing and economic instruments and capacity building as discussed in the conclusions.

Hydrocarbons are traditional subjects to European Union (EU) law (“acquis communitaire”). A short historical review reveals that quasi all aspects of upstream and downstream segments are covered by the legislation. The results of applied information extraction and elaborated quantitative analysis indicate that the intensity of legislation making correlates with global drivers such as oil price booms, and technology developments such as extraction of unconventional hydrocarbons by hydraulic fracturing. A quarter of a century after the Hydrocarbons Directive was published and transposed by Member States (MS), data allow us to make a semi-quantitative assessment on the implementation, the major drivers of governments’ publication activity, and the impact on the oil and gas production. Another specific relevance of this study is on non-energy minerals management of the EU, whether the introduction of similar competitive bidding rules would induce a greater interest of investors, and the enhanced competition could bring more benefits to the states by the rejuvenation of the critical minerals extractive sector. The preliminary findings show that in some MS there is a positive correlation between the concession call publication activity and hydrocarbons production. To confirm these conclusions the analysis of an extended dataset including exploration data, investments, and social impacts is needed in order to screen the effect of global market trends, the exhaustion of domestic geological reserves, and the different policy environments.