“…Renewable-energy innovation models therefore also include the market size for electricity and energy prices (Noailly and Smeets, 2013;Popp, 2002) to account for market conditions. Further, innovation diffusion and spillovers have to be distinguished from the effect of a country's policies or conditions (Noailly and Shestalova, 2013;Peri, 2005;Dechezleprêtre et al, 2013;Glachant et al, 2010). Additionally, models account for the impact of more general control variables like patent or knowledge stocks, resources, institutions, conditions for adoption of new technologies, innovation capacity of a country, trade and FDI inflows and the general size of the economy (additionally to the above, Spencer et al, 2015;Grübler and Wilson, 2014).…”