Fourth, they are more modular and can be deployed in a much more distributed fashion.
Fifth, unlike fossil or nuclear fuels, wind and sunlight cannot be transported, and while renewable energy resources are available in many areas, the best resources are frequently located at a distance from load centres thus, in some cases, increasing connection costs.
Technology to utilise the forces of nature for doing work to supply human needs is as old as the first sailing ship.
But attention swung away from renewable sources as the industrial revolution progressed on the basis of the concentrated energy locked up in fossil fuels.
The major published study on EROI, by Weissbach (2013) showed: “Nuclear, hydro, coal, and natural gas power systems (in this order) are one order of magnitude more effective than photovoltaics and wind power.” This raises questions about the sustainability of wind and solar PV which have not yet been addressed in national energy policies.
A fuller account of EROI in electricity generation is in the information paper on Energy Return on Investment.The (WEO2016) makes the points that VRE have five technical properties that make them distinct from more traditional forms of power generation.First, their maximum output fluctuates according to the real-time availability of wind and sunlight.Second, such fluctuations can be predicted accurately only a few hours to days in advance.Third, they are non-synchronous and use devices known as power converters in order to connect to the grid (this can be relevant in terms of how to ensure the stability of power systems).The costs of all these, over and above the generation costs, comprise the system costs.Grid-level system costs for VRE where they replace dispatchable sources are large (-80/MWh) but depend on country, context and technology (onshore wind Policies which favour renewables over other sources may also be required.Wind turbines have developed greatly in recent decades, solar photovoltaic technology is much more efficient, and there are improved prospects of harnessing the energy in tides and waves.Solar thermal technologies in particular (with some heat storage) have great potential in sunny climates.With government encouragement to utilise wind and solar technologies, their costs have come down and are now in the same league per kilowatt-hour as the increased costs of fossil fuel technologies, especially with likely carbon emission charges on electricity generation from them.However, the variability of wind and solar power does not correspond with most demand, and as substantial capacity has been built in several countries in response to government incentives, occasional massive output from these sources creates major problems in maintaining the reliability and economic viability of the whole system.