Northern Climate System Types

FLORIDA SOLAR ENERGY CENTER

Creating Energy Independence Since 1975

A Research Institute of the University of Central Florida

Northern Climate System TypesNorthern Climate System Types

System TypesSystem TypesSystem TypesSystem Types

ActiveActive Uses a pumpUses a pump

PassivePassive Does not use a pump – relies on natural forcesDoes not use a pump – relies on natural forces

Active SystemActive SystemActive SystemActive System

A pump circulates heat transfer liquid through the collector.

Solar collectorSolar collectorSolar collectorSolar collector

System typesSystem typesSystem typesSystem types

DirectDirect City potable (or well) water is circulated from the tank City potable (or well) water is circulated from the tank

to the collector and backto the collector and back For warm climatesFor warm climates

IndirectIndirect Fluid circulating through the collector never comes in Fluid circulating through the collector never comes in

contact with the city potable water in the storage tankcontact with the city potable water in the storage tank A heat exchanger is used to transfer heat from the A heat exchanger is used to transfer heat from the

circulating fluid to the potable watercirculating fluid to the potable water For cold climates - freezeFor cold climates - freeze

System typesSystem typesSystem typesSystem types

Available System TypesAvailable System TypesAvailable System TypesAvailable System Types

Active indirect using a differential controller Active indirect using a differential controller and flat plate collectorsand flat plate collectors

Active indirect drainback using a differential Active indirect drainback using a differential controllercontroller

Indirect thermosiphonIndirect thermosiphon

Closer look at each systemCloser look at each systemCloser look at each systemCloser look at each system

What makes the system uniqueWhat makes the system unique Basic operation and componentsBasic operation and components Freeze prevention mechanismsFreeze prevention mechanisms Maintenance requirementsMaintenance requirements Advantages and disadvantages of direct and Advantages and disadvantages of direct and

indirect systemsindirect systems

Thermosiphon SystemThermosiphon SystemThermosiphon SystemThermosiphon System




Passive systemPassive system No pump or controllerNo pump or controller

Thermosiphon actionThermosiphon action

Simple, reliable systemSimple, reliable system


Considerations Considerations ++ Simplicity, ease of understanding by service Simplicity, ease of understanding by service

personnelpersonnel Most common system internationallyMost common system internationally

Considerations -Considerations - InstallationInstallation Weight on roofWeight on roof Heat transfer fluids – periodic checkHeat transfer fluids – periodic check

Active Indirect SystemActive Indirect System

Active Indirect SystemActive Indirect SystemActive Indirect SystemActive Indirect System

Two typesTwo types Indirect using a Indirect using a

Heat exchangerHeat exchangerDifferential controller Differential controller Anti-freeze solutionAnti-freeze solution

Indirect drainback using a Indirect drainback using a Heat exchangerHeat exchangerDifferential controllerDifferential controllerDrainage of fluid from collectorDrainage of fluid from collector

Indirect DrainbackIndirect DrainbackIndirect DrainbackIndirect Drainback

Key feature is that the heat transfer liquid in Key feature is that the heat transfer liquid in the collector and collector loop drains back the collector and collector loop drains back into a drainback reservoirinto a drainback reservoir

When drained, there is no liquid in the collector When drained, there is no liquid in the collector to freezeto freeze


System includes a drainback reservoirSystem includes a drainback reservoir Also uses a differential controlled to regulate pump Also uses a differential controlled to regulate pump

operationoperation Heat exchanger is also incorporated into the system. Heat exchanger is also incorporated into the system.

Can be:Can be: Within the drainback reservoirWithin the drainback reservoir Within the solar tankWithin the solar tank

Collector and collector loop piping must be sloped to Collector and collector loop piping must be sloped to allow proper drainback allow proper drainback



Drainback reservoir


Freeze protection Freeze protection All fluid drains from the collector and collector All fluid drains from the collector and collector

looploop Fail safe method but piping and collector must Fail safe method but piping and collector must

be sloped to allow complete drainagebe sloped to allow complete drainage In colder climates glycol is mixed with water for In colder climates glycol is mixed with water for

added freeze securityadded freeze security


Considerations +Considerations +

Positive freeze protectionPositive freeze protection

Thermal energy from collector is conserved in Thermal energy from collector is conserved in drainback tanks – not lost in exposed drainback tanks – not lost in exposed collectorscollectors


Considerations –Considerations – Collectors have to withstand dry stagnationCollectors have to withstand dry stagnation Required elevation differences between Required elevation differences between

collectors and drainback tankscollectors and drainback tanks Higher collector loop pump capacity requiredHigher collector loop pump capacity required Collector and piping must be carefully installed Collector and piping must be carefully installed

to provide positive drainto provide positive drain

Indirect Pumped SystemIndirect Pumped System

Indirect Pumped SystemIndirect Pumped SystemIndirect Pumped SystemIndirect Pumped System

Use where freezing is commonUse where freezing is common Anti-freeze heat transfer fluidAnti-freeze heat transfer fluid Heat exchangerHeat exchanger

Internal or externalInternal or external Expansion tankExpansion tank Differential controllerDifferential controller Various valvesVarious valves



Considerations +Considerations + Freeze protection provided by anti-freeze fluidFreeze protection provided by anti-freeze fluid

glycolsglycols Collector loop remains full and pressurizedCollector loop remains full and pressurized Careful sloping of piping is not criticalCareful sloping of piping is not critical


Heat transfer properties of antifreeze fluids inferior to Heat transfer properties of antifreeze fluids inferior to water – reduced performancewater – reduced performance

Periodic maintenance required to ensure heat transfer Periodic maintenance required to ensure heat transfer fluid properties have not deterioratedfluid properties have not deteriorated

Collectors and antifreeze have to withstand stagnation Collectors and antifreeze have to withstand stagnation when summer load is satisfied early in daywhen summer load is satisfied early in day

Venting through T-P valve under stagnation Venting through T-P valve under stagnation conditionsconditions If excessive will require refilling of system to proper If excessive will require refilling of system to proper

operating pressureoperating pressure

System CertificationSystem CertificationSystem CertificationSystem Certification

Systems installed should be certified to Systems installed should be certified to insure product safety and proper design insure product safety and proper design

Florida Solar Energy Center (Florida)Florida Solar Energy Center (Florida)www.fsec.ucf.eduwww.fsec.ucf.edu

Solar Rating & Certification Corporation Solar Rating & Certification Corporation (National)(National)www.solar-rating.orgwww.solar-rating.org

Listing of Renewable Listing of Renewable EnergyEnergy

Listing of Renewable Listing of Renewable EnergyEnergy

www.dsireusa.orgDSIRE is a comprehensive source of information on state, local, utility, and federalincentives that promote renewable energy and energy efficiency.

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Northern Climate System Types