SOLAR HEATING

1
SOLAR HEATING

• Solar energy can be used for
• Solar water heating
• Solar space heating
• Solar pool heating

2
Solar Water Heating
3
Active solar water heaters

• Active solar water heaters rely on electric
  pumps, and controllers to circulate water.
• Active solar water-heating systems
• Direct-circulation systems
• Indirect-circulation systems

4
Passive solar water heaters

• The two most popular types of passive systems
  are
• Thermosyphon systems
• Integrated solar collectors

5
Solar Water Heating Applications

• Swimming pools
• Hot tubs and spas
• Domestic hot water
• Offices, malls, hotels, motels
• Large laundries and kitchens
• Facilities in remote areas
• Jails, hospitals and dormitories

6
Solar Water Heating Applications

• Process hot water
• Food processing, hot water cleanup
• Hot water rinses
• Pre-heat boiler makeup water

7
Value of Solar Water Heating

• Solar water heating systems
• Directly substitute renewable energy for
  conventional energy
• Reduce the amount of heat that must be provided
  by conventional water heating
• Reduce the use of electricity or fossil fuels by
  as much as 80.

8
Status of Solar Water Heating

• Todays solar water heating systems are well
  proven and reliable when correctly matched to
  climate and load.
• Solar water heating systems are most likely to be
  cost effective for facilities with expensive
  energy, or facilities with large hot water
  requirements.

9
Types of Collectors

• Low temperature to 32ºC
• Unglazed absorbers
• Mid temperature to 70ºC
• Glazed flat plate collectors
• Integrated collector systems (ICS), thermosyphon,
  antifreeze, drainback
• High temperature
• Evacuated tube to 175ºC
• Parabolic trough to 300ºC

10
Absorber plates

• There are various designs
• Bonded sheet design
• Tubes soldered or brazed to the plate
• Tubes fastened by clips, clamps or twisted wires.

11
Flat-plate Collector
12
Exploded view of flat plate collector
13
Passive, Indirect Thermosyphon System
14
Evacuated Tube Collector
15
Evacuated-tube collector
http//www1.eere.energy.gov/solar/printable_versio
ns/sh_basics_collectors.html
16
Two Main Types of Passive Systems

• Integrated Collector Systems (ICS)
• store the water in the collector itself
• Thermosyphon Systems
• have a separate storage tank directly above the
  collector

17
Two Main Types of Passive Systems (cont.)

• Good insulation of the collector and/or tank
  helps prevent heat loss at night, and helps
  prevent freezing.
• Connection pipes are the most critical parts for
  concern over freezing. Good insulation is
  necessary, but still does not totally solve the
  problem.

18

• The most frequently used systems for large
  facilities antifreeze systems are active,
  indirect systems.
• System configurations may utilize one storage
  tank or two tanks.
• Single tank conventional h/w heater
• Single tank wrap-around heat exchanger
• Two tank convection flow

19

• The most cost-effective size for a solar water
  heating system is typically to meet the full
  summer demand, but to meet only 2/3 of the
  year-round demand.
• Meeting the full winter demand with the reduced
  solar resource is very costly.
• Experience with commercial buildings seems to
  show that maximum cost-effectiveness occurs at a
  solar supply of about 50 of the year-round
  demand.

20
Efficiency Aspects of Solar Water Heating

• Colder water supply temperatures increase system
  efficiency, since the fluid being heated loses
  less heat to the surrounding air until it reaches
  higher temperatures.
• Colder air temperatures reduce system efficiency
  by increasing the loss of heat from the
  collectors to the air.
• Potential for system freezing is a serious
  problem, and many solutions result in reducing
  system efficiency.

21
Solar water heating in Cyprus

• A few islands are using solar water heaters on a
  very large scale (Barbados and Cyprus).
• Cyprus is a leading country in installed solar
  collectors per capita - 0.86 m² of solar
  collector per capita.
• Solar water heaters were first fabricated and
  installed in 1960.

22
Solar water heating in Cyprus

• The majority of solar domestic hot water heaters,
  put up on individual houses are of the
  thermosyphon type.
• Two solar collectors, with a total glazed area of
  3 square meters, are connected in series to a hot
  water tank, placed at a height, just above the
  top of collectors.
• The hot water tank is also fitted with an
  auxiliary electric 3 kW heater.

23
Economics of Solar water heating in Cyprus

• The average daily solar radiation falling on a
  collector installed at an angle of 35 to the
  horizontal in Cyprus is 5.4 kWh per m2.
• the annual savings per square meter of installed
  collector area in Cyprus are 550 kWh.
• The total cost required to install a solar water
  heating system on a house is around US 1000.
• The payback period is estimated to be 4 years

24
Conservation

• Conservation is usually the most cost-effective
  way to reduce water-heating bills.
• - For example, a low-flow showerhead saves 200
  kWh of electrical energy (USD 40).

25
Solar space heating and cooling

• Solar energy can heat and cool the air
• Solar space heating systems
• Passive
• Active
• Combination

26
Air Heating

• Air or other gases can be heated with FPC
• The principal requirement is a large contact area
  between plate and air
• Extended surfaces are used to counteract the low
  heat transfer coefficients between metal and air.
• Metal or fabric matrices or corrugated metal
  sheets improve performance

27
Solar air collector
Air flat-plate collectors are used for space
heating.
http//www1.eere.energy.gov/solar/printable_versio
ns/sh_basics_collectors.html
28
Transpired air collectors

• A transpired air collector preheats air for
  building ventilation by using a fan to draw fresh
  air through the system.
• They are very efficient
• No glazing
• Transpired air collectors are recommended for
  industrial or commercial buildings with large
  ventilation requirements.

29
Air heating

• Transpired air collectors
• http//www.eere.energy.gov/de/transpired_air.html

30
Winter operation
31
Summer operation