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Chapter 3

be analyzed precisely after collecting reliable measurement data with sufficient time resolution and time synchronization. The results will con- tribute to the economic and reliable integration of PV into the energy system.

3.5.4

Concentrating solar power generation characteristics and grid stabilization

In a CSP plant, even without integrated storage, the inherent thermal mass in the collector system and spinning mass in the turbine tend to significantly reduce the impact of rapid solar transients on electrical out- put, and thus, lead to less impact on the grid (also see Section 8.2.1). By including integrated thermal storage systems, base-load capacity factors can be achieved (IEA, 2010b). This and the ability to dispatch power on demand during peak periods are key characteristics that have motivated regulators in the Mediterranean region, starting with Spain, to support large-scale deployment of this technology with tailored FITs. CSP is suit- able for large-scale 10- to 300-MWe plants replacing non-renewable thermal power capacity. With thermal storage or onsite thermal backup (e.g., fossil or biogas), CSP plants can also produce power at night or when irradiation is low. CSP plants can reliably deliver firm, scheduled power while the grid remains stable.

CSP plants may also be integrated with fossil fuel-fired plants such as displacing coal in a coal-fired power station or contributing to gas- fired integrated solar combined-cycle (ISCC) systems. In ISCC power plants, a solar parabolic trough field is integrated in a modern gas and steam power plant; the waste heat boiler is modified and the steam turbine is oversized to provide additional steam from a solar steam generator. Better fuel efficiency and extended operating hours make combined solar/fossil power generation much more cost-effective than separate CSP and combined-cycle plants. However, without including thermal storage, solar steam could only be supplied for some 2,000 of the 6,000 to 8,000 combined-cycle operating hours of a plant in a year. Furthermore, because the solar steam is only feeding the combined-cycle turbine—which supplies only one-third of its power—the maximum solar share obtainable is under 10%. Nonetheless, this concept is of special interest for oil- and gas-producing sunbelt countries, where solar power technologies can be introduced to their fossil-based power mar- ket (SolarPACES, 2008).

3.6

Environmental and social impacts6

This section first discusses the environmental impacts of direct solar technologies, and then describes potential social impacts. However, an overall issue identified at the start is the small number of peer-reviewed studies on impacts, indicating the need for much more work in this area.

6

A comprehensive assessment of social and environmental impacts of all RE sources covered in this report can be found in Chapter 9.

Direct Solar Energy

3.6.1

Environmental impacts

No consensus exists on the premium, if any, that society should pay for cleaner energy. However, in recent years, there has been progress in analyzing environmental damage costs, thanks to several major projects to evaluate the externalities of energy in the USA and Europe (Gordon, 2001; Bickel and Friedrich, 2005; NEEDS, 2009; NRC, 2010). Solar energy has been considered desirable because it poses a much smaller environ- mental burden than non-renewable sources of energy. This argument has almost always been justified by qualitative appeals, although this is changing. Results for damage costs per kilogram of pollutant and per kWh were presented by the International Solar Energy Society in Gordon (2001). The results of studies such as NEEDS (2009), summarized in Table 3.3 for PV and in Table 3.4 for CSP, confirm that RE is usually comparatively beneficial, though impacts still exist. In comparison to the figures pre- sented for PV and CSP here, the external costs associated with fossil generation options, as summarized in Chapter 10.6, are considerably higher, especially for coal-fired generation.

Considering passive solar technology, higher insulation levels provide many benefits, in addition to reducing heating loads and associated costs (Harvey, 2006). The small rate of heat loss associated with high levels of insulation, combined with large internal thermal mass, creates a more comfortable dwelling because temperatures are more uniform. This can indirectly lead to higher efficiency in the equipment supply- ing the heat. It also permits alternative heating systems that would not

2005 2025

2050

0.17

0.14

0.10

0.01

0.01

0.01

0.00

0.00

0.00

0.00

0.00

0.00

N/A

0.01

0.01

0.18

0.17

0.12

Table 3.3 | Quantifiable external costs for photovoltaic, tilted-roof, single-crystalline sili- con, retrofit, average European conditions; in US2005 cents/kWh (NEEDS, 2009).

Health Impacts Biodiversity Crop Yield Losses Material Damage Land Use Total

2005

2025

2050

0.65

0.10

0.06

0.03

0.00

0.00

0.00

0.00

0.00

0.01

0.00

0.00

N/A

N/A

N/A

0.69

0.10

0.06

Table 3.4 | Quantifiable external costs for concentrating solar power; in US2005 kWh (NEEDS, 2009).

Health Impacts Biodiversity Crop Yield Losses Material Damage Land Use Total

cents/

369

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