Renewable Energy I Passive solar Active solar Large-scale solar thermal Solar photovoltaic – residential, commercial Wind power Biomass

Passive solar – design, siting. In spite of 40 years of availability of tried and true designs, less than 10% of new single-family dwellings meet passive solar standards. Cost? Acceptance?

Active solar collection for residences is cost-effective in most parts of the US. Tax incentives make the payback period economically advantageous. However these tax advantages come and go with budget and political pressure.

content/uploads/2009/02/brightsource-heliostats-and-power-tower.jpg Large-scale solar-thermal systems utilize Stiller heat engine or steam-to-turbine systems to power electrical generators. Solar power is predictably time-variable, and must be accompanied by storage back-up (pump-storage hydroelectric, for example). Alternative capacity from fossil or nuclear systems is generally assumed to be required for large utility-supplying systems.

Large-scale solar collection systems impact land use and ecosystems. Often, these environments are otherwise considered ‘waste’ land.

The economics of solar photovoltaic power generation at the medium and small scale depend on state-level regulations that support ‘reverse metering’ allowing the owner to be paid for power entering the utility grid. Without these regulations, investment in solar photovoltaics may not be economically viable. A key factor in the economics of investment in solar photovoltaic systems is the payback period given the initial investment. Payback may not occur at all if the system requires large battery storage, increasing the cost to levels such that the payback period exceeds the replacement time of solar cell and battery components.

Solar photovoltaic systems are available at residential and commercial scale. For large-scale systems, land-use impacts are considerable. The environmental impact of solar cell manu- facture has come under scrutiny, although with appropriate safeguards, the impacts are minor.

Capacity factors are a key measure used to assess the availability of power to grid systems. Fossil fuel and nuclear power plants have capacity factors in the 90% range For wind and solar, capacity factors are in the 15-20% range. This means that wind and solar sources must be systematically overbuilt to assure a robust power supply, or the renewable sources must be backed-up by fossil fuel plants. Natural gas-fired turbine systems are particularly useful as back-up power sources.

-wind-turbine.gif prairieroots.files.wordpress.com/2007/10/moja.. The ‘beauty’ of wind towers is very much in the eye of the beholder. In most areas where surveys are done in advance of wind farm development, about 35% of the population favors wind farms; about 35% are opposed for various reasons, mostly aesthetic, and the rest, about 30%, have no opinion. In many areas, local municipalities face difficult political choices as strong pro and con views emerge among local landowners. In rural areas, leasing of space for wind farm development is an important source of income.

The incidence of bird (raptor) and bat deaths related to wind towers is a factor that must be considered in wind farm placement. These impacts have been used as an argument against wind farm development in some areas. In most areas that have been studied, wind farms do not have a negative impact on property values. However, these studies are all relatively short-term.

Biomass: carbon-neutral (ideally) – land use concerns combustible renewable wastes - ~10% of total world energy production wood waste landfill gas municipal solid waste manure biogas waste cooking oil – biodiesel cropland biomass – ‘energy plantations’ fast-growing tree/grass species – willow, switchgrass biodiesel – oil seed crops ethanol – corn, wheat algal biomass

Biomass – concerns biofuels competition with food crops degree of carbon-neutrality soil degradation cropland and forest biomass monoculture – pests, loss of bioodiversity loss of habitat land use changes