Direct forms of solar energy

1

direct forms of solar energy solar

annual Sun’s radiation solar

Source: https://doi.org/10.1016/j.rser.2016.05.022

annual Sun’s radiation solar

June December

Source: PVGIS © European Communities, 2001-2008

Portugal: 7 - 7.6 kWh/m2 Portugal: 1.6 - 2.2 kWh/m2

2 times central Europe+30% central Europe

summerwinter

S

v v

S

N W

E

↵S

'S'S

↵S

N W

E

Sun’s path solar

mid latitude at North hemisphere

altitude azimuth

solar technologies solar

low temperature solar collectors

concentration solar power

solar photovoltaic

Low temperature solar collectors

6

Low temperature solar collectors solar

glazed flat plane collector solar

Pumped solar system solar

thermosiphon solar system solar

evacuated solar tubes solar

world thermal power capacity solar

world thermal power capacity solar

47

02

Source: See Endnote 7 for this section.

Source: See Endnote 7 for this section.

Source: See Endnote 9 for this section.

China 68%

Germany 4.6%Turkey 4.6%Brazil 1.7%India 1.5%Japan 1.5%Israel 1.3%Austria 1.3%Greece 1.3%Italy 0.9%Australia 0.8%Spain 0.8%

Rest of World 11.3%

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

250

200

150

100

50

0

Gigawatts-thermal

79

195223

68

255

171148

124

595144

91105

Note: Data are for glazed water collectors only. preliminary

Turkey 2.6%Germany 1.8%India 1.5%Brazil 0.7%Italy 0.6%Israel 0.5%Australia 0.4%Spain 0.4%Poland 0.4%France (mainland) 0.3%Austria 0.3%

Rest of World 7.9%

China 83%

TOTAL ADDED ~ 49 GWth

FIGURE 15. SOLAR WATER HEATING GLOBAL CAPACITY ADDITIONS, SHARES OF TOP 12 COUNTRIES, 2011

SOLAR THERMAL HEATING

FIGURE 16. SOLAR WATER HEATING GLOBAL CAPACITY, SHARES OF TOP 12 COUNTRIES, 2011

TOTAL CAPACITY ~ 223 GWth

FIGURE 17. SOLAR WATER HEATING GLOBAL CAPACITY, 2000–2012

Area: 70 x 106 m2

Ti

Tf

m

Flate plate collector solar

mass [kg]

fluid thermal capacity [J/(kgK)]

output temperature [K]

input temperature [K]

[J] Q = mc(Tf � Ti)Q = mc(Tf � Ti) [W]

m

c

m mass flow [kg/s]

Tf

Ti

heating energy/power solar

⌧↵

⇢

⇢

thermal lossesG

collector efficiency solar

thermal losses

thermal losses

optical losses

constituents, such as Fe2O3. Figure 4.81 gives an example of the wavelengthdependence of the transmittance, τλ, through ordinary window glass, definedas the fraction of incident light that is neither reflected [cf. (3.12)] norabsorbed,

τλ = 1− ρλ − αλ: (4.111)

For a collector of the type considered, multiple reflections may take placebetween the absorber and the cover system as well as within the cover sys-tem layers, if there is more than one. The reflections are mostly specular(angle of exit equal to angle of incidence) at glass surfaces, but mostly dif-fuse (hemispherically isotropic) at the absorber surface. Thus, the amount ofradiation absorbed by the absorber plate, in general, cannot be calculatedfrom knowledge of the total incoming flux but must be calculated for each

1

0.5

Abs

orpt

ance

al=

e l

00.5 1 2

Wavelength (10−6m)

5 10

FIGURE 4.80 Spectral absorptance (or emittance) of a commercial “black chrome” type ofselective surface. (Based on Masterson and Seraphin, 1975.)

0.50

0.5

Tran

smitt

ance

tl

1

1Wavelength (10−6m)

2 5 10

FIGURE 4.81 Spectral transmittance, (1 ρλ αλ), of 2.8 × 10−3 m thick glass layer with a Fe2O3

content of 0.1. (Based on Dietz, 1954.)

4.4 Solar Radiation Conversion 455

espectral absorptivity of selective surfaces solar

decreasethermal losses

decreaseoptical losses

constituents, such as Fe2O3. Figure 4.81 gives an example of the wavelengthdependence of the transmittance, τλ, through ordinary window glass, definedas the fraction of incident light that is neither reflected [cf. (3.12)] norabsorbed,

τλ = 1− ρλ − αλ: (4.111)

For a collector of the type considered, multiple reflections may take placebetween the absorber and the cover system as well as within the cover sys-tem layers, if there is more than one. The reflections are mostly specular(angle of exit equal to angle of incidence) at glass surfaces, but mostly dif-fuse (hemispherically isotropic) at the absorber surface. Thus, the amount ofradiation absorbed by the absorber plate, in general, cannot be calculatedfrom knowledge of the total incoming flux but must be calculated for each

1

0.5

Abs

orpt

ance

al=

e l

00.5 1 2

Wavelength (10−6m)

5 10

FIGURE 4.80 Spectral absorptance (or emittance) of a commercial “black chrome” type ofselective surface. (Based on Masterson and Seraphin, 1975.)

0.50

0.5

Tran

smitt

ance

tl

1

1Wavelength (10−6m)

2 5 10

FIGURE 4.81 Spectral transmittance, (1 ρλ αλ), of 2.8 × 10−3 m thick glass layer with a Fe2O3

content of 0.1. (Based on Dietz, 1954.)

4.4 Solar Radiation Conversion 455

espectral transmissivity of the glazing surface solar

opaque tolongwaveradiation

transparent toshortwaveradiation

GAcQu

optical losses thermal losses⇢GAc + (Tabs � Tamb)UAt

Qu = GAc � ⇢GAc � (Tabs � Tamb)UAt

collector useful energy solar

available solar energy

usefulenergy

losses

⌘ = ⌘0 �↵1�T

G

⌘0

�T

G=

⌘0↵1

�T

G

⌘ ⌘ = (1� ⇢)� UAt

Ac

�T

G Tabs ' Tf

Tamb ' Ti

�T = Tf � Ti

dU

dT= 0

Assumptions

collector efficiency solar

�T

G

⌘

Optical efficiency

Saturation temperature efficiency

collector efficiency solar

�T

G

⌘

optical losses100%

thermal losses

collector efficiency solar

solar collector efficiency solar

water-to-external air temperature difference

effici

ency

⌘ = ⌘0 � ↵1�T/G� ↵2�T 2/G

(G=800 W/m2)

Ti

Tf

Qu

useful energy

solar collector efficiency solar

• solar collector efficiency • pipes thermal losses • storage tank thermal losses

QuQ

sol

system efficiency solar

Qi

Qf

Qaux

Qu

= Qf

�Qi

�Qaux

Qsol

⌘ =Q

u

Qsol

system efficiency solar

Qi

Qf

Qaux

Qsol

FS =Qu

Qn

Energy needsQn = Qf �Qi

solar fraction solar

low water temperature for swimming pools (no storage tank needed) evaporator component of heat pump

unglazed solar collectors solar

installed solar collectors by type solar

55

02

Notes: Costs are indicative economic costs, levelised, and exclusive of subsidies or policy incentives. Several components determine the levelised costs of energy (LCOE), including: resource quality, equipment cost and performance, balance of system/project costs (including labour), operations and maintenance costs, fuel costs (biomass), the cost of capital, and productive lifetime of the project. The costs of renewables are site specific, as many of these components can vary according to location. Costs for solar electricity vary greatly depending on the level of available solar resources. It is important to note that the rapid growth in installed capacity of some renewable technologies and their associated cost reductions mean that data can become outdated quickly; solar PV costs, in particular, are changing rapidly. Costs of off-grid hybrid power systems that employ renewables depend largely on system size, location, and associated items such as diesel backup and battery storage. Data for rural energy are unchanged from GSR 2011, with the exception of wind turbines. i Litre of diesel or gasoline equivalent Source: See Endnote 99 in Wind Power section for sources and assumptions.

TABLE 2. STATUS OF RENEWABLE ENERGY TECHNOLOGIES: CHARACTERISTICS AND COSTS (CONTINUED)

Technology Typical Characteristics Capital Costs Typical Energy Costs (USD/kW) (LCOE – U.S. cents/kWh)

Transport Fuels Feedstocks Feedstock characteristics Production costs (U.S. cents/litre)i

BiodieselSoy, rapeseed, mustard seed, palm, jatropha, waste vegetable oils, and animal fats

Range of feedstocks with different crop yields per hectare; hence, production costs vary widely among countries. Co-products include high-protein meal.

Soybean oil: 45-90 (Argentina/USA) Palm oil: 30–100 (Indonesia/Malaysia/Thailand/Peru)Rapeseed oil: 120–140 (EU)

EthanolSugar cane, sugar beets, corn, cassava, sorghum, wheat (and cellulose in the future)

Range of feedstocks with wide yield and cost variations. Co-products include animal feed, heat and power from bagasse residues. Advanced biofuels are not yet fully commercial and have higher costs.

Sugar cane: 45–80 (Brazil)Corn (dry mill): 60–120 (USA)

Biogas digester Digester size: 6–8 m3 n/a

Biomass gasifier Size: 20–5,000 kW LCOE: 8–12

Solar home system System size: 20–100 W LCOE: 40–60

Household wind turbine Turbine size: 0.1–3 kWCapital cost: 10,000/kW (1 kW turbine); 5,000/kW (5 kW); 2,500/kW (250 kW) LCOE: 15–35+

Village-scale mini-grid System size: 10–1,000 kW LCOE: 25–100

Technologies Typical characteristics Installed costs (USD/kW) or LCOE for Rural Energy (U.S. cents/kWh)

Hot Water/Heating/Cooling (continued)

Solar thermal: Domestic hot water systems

Collector type: flat-plate, evacuated tube (thermosiphon and pumped systems)Plant size: 2.1–4.2 kWth (single family); 35 kWth (multi-family)Efficiency: 100%

Single-family: 1,100–2,140 (OECD, new build); 1,300–2,200 (OECD, retrofit) 150–635 (China) Multi-family: 950–1,850 (OECD, new build); 1,140–2,050 (OECD, retrofit)

1.5–28 (China)

Solar thermal: Domestic heat and hot water systems (combi)

Collector type: same as water onlyPlant size: 7–10 kWth (single-family); 70–130 kWth (multi-family); 70–3,500 kWth (district heating); >3,500 kWth (district heat with seasonal storage)Efficiency: 100%

Single-family: same as water onlyMulti-family: same as water onlyDistrict heat (Europe): 460–780; with storage: 470–1,060

5–50 (domestic hot water) District heat: 4 and up (Denmark)

Solar thermal: Industrial process heat

Collector type: flat-plate, evacuated tube, parabolic trough, linear FresnelPlant size: 100 kWth–20 MWthTemperature range: 50–400° C

470–1,000 (without storage) 4–16

Solar thermal: CoolingCapacity: 10.5–500 kWth (absorption chillers); 8–370 kWth (adsorption chillers)Efficiency: 50–70%

1,600–5,850 n/a

costs solar

OUTROS SISTEMAS SOLARES

DESTILADOR SOLAR

PAREDES DE ACUMULAÇÃO

FORNO SOLAR

BIBLIOGRAFIA

Ehrlich, R. Renewable Energy, a first course Solar Thermal (10.1 a 10.5, 10.8, 10.11)

Boyle, G. Renewable Energy, Power for Sustainable Future Solar Thermal Energy (2.6, 2.10)