Sustainable Energy Systems Sustainable Energy Systems EngineeringEngineering

Peter GevorkianPeter Gevorkian

Ch 8: Passive Solar Heating Ch 8: Passive Solar Heating TechnologyTechnology

Brevard Community CollegeBrevard Community College

ETP1401ETP1401

Bruce HesherBruce Hesher

Passive Solar (also called solar Passive Solar (also called solar thermal) heating refers to exposing thermal) heating refers to exposing water or other fluids directly to the water or other fluids directly to the sun in order to heat them, instead of sun in order to heat them, instead of using electricity or other fuels.using electricity or other fuels.

Efficiencies can be higher (up to Efficiencies can be higher (up to 70%) than using other technologies 70%) than using other technologies that have more conversion steps.that have more conversion steps.

This is the “low hanging fruit” of the renewable This is the “low hanging fruit” of the renewable energy market. While photovoltaic systems are energy market. While photovoltaic systems are gaining traction, most solar installations, as of gaining traction, most solar installations, as of 2011, are solar water heating systems. Why? 2011, are solar water heating systems. Why? Paybacks are shorter (3-5 versus 8-10 years) and Paybacks are shorter (3-5 versus 8-10 years) and initial investment is lower.initial investment is lower.

Solar Thermal UsesSolar Thermal Uses

Solar Thermal Technology can be used for many Solar Thermal Technology can be used for many purposes including:purposes including:

•Solar Water Heating (domestic and commercial)Solar Water Heating (domestic and commercial)

•Swimming Pool HeatingSwimming Pool Heating

•Space HeatingSpace Heating

NoteNote: the word “: the word “passivepassive” has multiple ” has multiple meaning in solar thermal systems. It can meaning in solar thermal systems. It can mean using the suns energy to heat fluids mean using the suns energy to heat fluids directly, and it can mean using the heat from directly, and it can mean using the heat from the sun to cause the fluids to circulate without the sun to cause the fluids to circulate without any other energy input (no pumps).any other energy input (no pumps).

Passive Solar Water HeatingPassive Solar Water Heating

Solar Water Heating (SWH) is mature technology that reduces the need to buy energy to heat water. After weatherization and conservation SWH is usually the next thing to consider.

As with most As with most renewable energy renewable energy technologies, SWH has technologies, SWH has high up front costs and high up front costs and low cost of operation. low cost of operation. The The payback is 3-5 years on equipment on equipment that that lasts over 20 years.

Flat Plate CollectorsFlat Plate Collectors

Flat plate collectors are made of copper pipe and painted black. They are in sealed boxes that let light in and prevent heat loss. They are much more efficient at capturing the suns energy than solar electric modules. 60-70% versus 12-22%!

They are placed on the They are placed on the roof in a location with good roof in a location with good southern exposure.southern exposure.

SWH System DiagramSWH System Diagram

Solar water heating systems are more complex than traditional electric or gas tanks but use free fuel!

About 25-30%25-30% of the typical electric bill is water heating. SWH systems cost about $3-4k.

The quality of the The quality of the installation makes a big installation makes a big difference!difference!

SWH System TypesSWH System Types

There are many different designs for different climates.There are many different designs for different climates.

A “A “directdirect” a.k.a. “” a.k.a. “open Loopopen Loop” system sends the potable ” system sends the potable water through the collector. An “water through the collector. An “indirectindirect” a.k.a. “” a.k.a. “closed loopclosed loop” ” system uses a heat exchange fluid (usually propylene system uses a heat exchange fluid (usually propylene glycol) in the collector and a heat exchanger.glycol) in the collector and a heat exchanger.

A “A “passivepassive” system uses the heat of the water to cause it to ” system uses the heat of the water to cause it to circulate. An “circulate. An “activeactive” system uses a pump(s). The pump ” system uses a pump(s). The pump may be powered by a wall socket or by a 10-20W solar may be powered by a wall socket or by a 10-20W solar module.module.

System TypesSystem Types

Many different system designs are possible depending on climate, capacity, performance, price and Etc.

In Florida direct, active systems are common. The In Florida direct, active systems are common. The BCC course BCC course ETP1420 Solar Thermal Systems ETP1420 Solar Thermal Systems covers SWH.covers SWH.

Closed loop Closed loop systems with propylene glycol in the collector loop are recommended for areas where freezing is possible.

Thermo-siphonThermo-siphon systems are inexpensive and reliable because they have few moving parts. But they require the storage tank to be above the collector Integrated Collector Systems Integrated Collector Systems “ICS” are only used where there is no chance of freezing.

Solar Pool HeatingSolar Pool Heating

Heat collectors made of black Heat collectors made of black plastic tubing panels placed plastic tubing panels placed on roof and in the return line on roof and in the return line from filter to pool from filter to pool add energyadd energy (heat) to the water.(heat) to the water.

A solar blanket on top of A solar blanket on top of the pool the pool cuts evaporative cuts evaporative heat lossheat loss which accounts which accounts for over for over 70% 70% of the total of the total heat losses.heat losses.

Solar Space HeatingSolar Space Heating

See See http://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm#Phttp://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm#Passive assive

Concentrating Solar Power Concentrating Solar Power CSP CSP p222p222

CSP is used in commercial CSP is used in commercial setting to generate electricity. A setting to generate electricity. A fluid usually oil is heated then fluid usually oil is heated then run through a heat exchanger to run through a heat exchanger to turn water into steam to run a turn water into steam to run a generator.generator.

Another method is to reflect Another method is to reflect sunlight onto a boiler and sunlight onto a boiler and heat it directly.heat it directly.

Solar CookersSolar Cookers

Parabolic dish solar cookers Parabolic dish solar cookers are effective ovens on sunny are effective ovens on sunny days.days.

They can reach temperatures They can reach temperatures over over 400°F400°F ! !

They fold down for easy storage They fold down for easy storage or transportation.or transportation.

Solar Cooling and Air Conditioning.Solar Cooling and Air Conditioning.

Cold is the absence of heat. The science that deals with Cold is the absence of heat. The science that deals with heat is thermodynamics. It has 2 basic laws:heat is thermodynamics. It has 2 basic laws:

1) 1) Conservation of energy: Energy can not be created or Conservation of energy: Energy can not be created or destroyed. However it can be converted from one form to destroyed. However it can be converted from one form to another.another.

2) 2) Energy is always transferred from a higher state to a Energy is always transferred from a higher state to a lower one. lower one.

There are There are 33 ways heat can transfer: ways heat can transfer: RadiationRadiation: ex. Sun to Earth: ex. Sun to Earth ConductionConduction: Heat transfer by physical contact.: Heat transfer by physical contact. ConvectionConvection: flow of heat between air, gas, liquid, or fluids.: flow of heat between air, gas, liquid, or fluids.

Cooling TechnologiesCooling Technologiesp228p228

There are 2 types of refrigeration technologies in use There are 2 types of refrigeration technologies in use electric vapor-compression electric vapor-compression (freon gas) and (freon gas) and heat driven heat driven absorption absorption cooling.cooling.

Absorption coolers are operated by steam, hot water, fossil Absorption coolers are operated by steam, hot water, fossil fuels or a combination. There are 2 types of absorption fuels or a combination. There are 2 types of absorption chillers that have been used for about 100 years:chillers that have been used for about 100 years:

1) Lithium Bromide LiBr1) Lithium Bromide LiBr: Uses LiBr as the energy : Uses LiBr as the energy conversion medium and water as a refrigerant. Can get conversion medium and water as a refrigerant. Can get down to about down to about 40°F.40°F.

2) Amonia chillers 2) Amonia chillers use ammonia as the energy conversion use ammonia as the energy conversion media and a mix of ammonia and water as the refrigerant. media and a mix of ammonia and water as the refrigerant. They can get down to about They can get down to about 20°F.20°F.

States of MatterStates of Matter

Most substances can exist as vapor, liquid, or a solid Most substances can exist as vapor, liquid, or a solid depending on temperature. When the substance depending on temperature. When the substance changes state heat is transferred. When liquids become changes state heat is transferred. When liquids become gases heat is absorbed (they get cold). When gases are gases heat is absorbed (they get cold). When gases are compressed into liquids heat is given off. compressed into liquids heat is given off.

This is why the This is why the compressor under compressor under a refrigerator a refrigerator gets warm and gets warm and has a cooling fan.has a cooling fan.

Coefficient of Performance “COP “Coefficient of Performance “COP “p228p228

The efficiency of an air conditioning systems is defined by The efficiency of an air conditioning systems is defined by the “COP” as the ratio of cooling energy to the energy the “COP” as the ratio of cooling energy to the energy supplied to the unit. supplied to the unit.

A ton of cooling energy is 12,000 British thermal Units A ton of cooling energy is 12,000 British thermal Units (btu’s) per hour. A cooling ton is also equal to 3514 Watts (btu’s) per hour. A cooling ton is also equal to 3514 Watts of electric power.of electric power.

A one ton air conditioning unit that consumes 1500W of A one ton air conditioning unit that consumes 1500W of electric power would have a COP of 3514W/1500W or electric power would have a COP of 3514W/1500W or 2.343.2.343.

Simplified diagram of a single effect Simplified diagram of a single effect absorption cycleabsorption cycle

    Efficiency and lower Efficiency and lower operating costs are operating costs are achieved through the use achieved through the use of a pump rather  than a of a pump rather  than a compressor and a heat compressor and a heat exchanger to recover and exchanger to recover and supply heat to the supply heat to the generator.generator.

Although the process is similar to conventional electric Although the process is similar to conventional electric vapor compression systems, absorption cooling vapor compression systems, absorption cooling substitutes a generator and absorber, called a thermal substitutes a generator and absorber, called a thermal compressor, for an electric compressor.compressor, for an electric compressor.

See http://www.gasairconditioning.org/absorption_how_it_works.htm

Direct Solar Power GenerationDirect Solar Power Generation

Solargenix Energy has developed a Concentrating Solar Solargenix Energy has developed a Concentrating Solar Power (CSP) generation facility in Red Rock Arizona that Power (CSP) generation facility in Red Rock Arizona that make about 1MW of power.make about 1MW of power.

Solargenix has advanced concentrating trough Solargenix has advanced concentrating trough technology in recent years: technology in recent years:

See NREL: Solargenix white paperSee NREL: Solargenix white paper

Innovations in Passive Solar Power Technology Innovations in Passive Solar Power Technology p230p230

Someone is always working on a new idea. Some of Someone is always working on a new idea. Some of them are good, some are not. Some make it to the them are good, some are not. Some make it to the market place some don’t. The text presents some ideas. market place some don’t. The text presents some ideas.

Sunflower 250: Sunflower 250: A solar PV system with tracking and A solar PV system with tracking and concentrating.concentrating.

Stirling Engine Sunflower: Stirling Engine Sunflower: A system with multiple mirrors A system with multiple mirrors concentrating heat to run a Stirling engine.concentrating heat to run a Stirling engine.

SunPod SunPod A PV system that uses a Fresnel lens to A PV system that uses a Fresnel lens to concentrate solar power.concentrate solar power.