Hot Water Storage

Each array is plumbed to its own 120 gallon hot water storage tank. The two

are kept separate to compare the performance of the two systems. The

outlets of each tank are then plumbed together so they can be used

together for heating and cooling of the building.

Yazaki Absorption Chiller

The Yazaki WFC SC10

provides 5 tons of cooling

capacity. These units are

currently not available for small

applications as they are more

expensive and complex that a

standard electric air

conditioning unit.

Heat Exchangers

Two heat exchangers are mounted directly beneath the furnace. The

cooling coil has the capability to remove 42,635 Btu/Hr from the air flow.

The coil is driven by chilled water from the absorption chiller at 10 gpm

and 45°F. The heating coil has the capability to provide 54,257 Btu/hr of

heat with a flow rate of 8 gpm water at 180° F.

Data Collection

A National Instruments Field Point Unit is

used to monitor temperatures and flows

throughout the system. This real-time data is

used to provide system and component

efficiencies as well as the amount of

greenhouse gases offset by the use of solar

thermal energy.

DRI plans to continue collaborative solar research in the following areas:

cost-effective flat plate solar collectors, flat plate solar collectors for

vapor-transport systems, small-scale combined heat and power (CHP)

collectors, testing of organic PV cells, concentrated solar power towers,

and solar driven thermoelectric generators..

The electricity required to run the system is drawn from the facility’s

renewable power systems. This includes: PV and wind turbines with

electrical storage in batteries and H2 which can later be combusted in an

internal combustion engine.

Located in Reno, Nevada, the DRI North campus is a prime candidate

to perform solar research. DRI has participated in both solar thermal

and solar electrical projects in recent years. Most of these solar

capabilities are now incorporated into DRI’s Renewable Energy

Experimental Facility (REEF). This includes solar thermal air collectors,

liquid/glycol collectors, and water collectors; in addition both tracking

and fixed to photovoltaic (PV) arrays. The REEF consists of a 1200 ft2

home and 600 ft2 workshop.

A practical and cost-effective method to utilize solar energy is to capture

solar radiation as heat. This energy can then be used in both heating

and cooling applications. Two types of solar thermal collectors have

been implemented into the REEF House: one roof mounted and the

other ground mounted.

Because potable water is passed through the Sunvelope collectors, this

eliminates costly components and complex heat exchange systems. The

flexibility allows for additional uses such as steam generation for

electricity production.

Fig. 1. REEF House Solar Thermal Collectors

The 200 sq. ft. array mounted

on the roof are Sunvelope

Solar collectors, made in

Sparks, NV. These collectors

utilize an “envelope” system

that allows them to expand

and contract with temperature

change. These collectors can

withstanding freezing and

boiling without the use of a

drainback system.

Fig. 2. Sunvelope Solar

Collectors

Fig. 3. REEF House HVAC System

Fig. 6. Heat exchangers and

furnace

The thermodynamic cycle of

absorption refrigeration is a

method of air conditioning that

can be driven by solar

applications. Figure 4

demonstrates how the system

operates. The principle is that a

refrigerant will absorb heat from

the conditioned space as it cools

due to evaporation.

System Control

Fig. 4. Thermodynamic Cycle

Fig. 5. Yazaki Absorption Chiller

A 200 sq. ft. array of Viessman glycol based

solar thermal collectors is ground mounted on

the south side of the house. The racking

system allows for manual adjustment from 10°-

62° The glycol based mixture heats water

through a heat exchanger mounted in a control

box.

System Configuration

Hot water is pumped from the

hot water storage tanks to

either an absportion chiller for

cooling or a heat

exchanger/coil located in the

house ductwork. A schematic

of the system is shown in

Figure 3.

The system is controlled by a thermostat,

similar to that used in any typical

residence. The thermostat is set for

heating mode and cooling mode. During

times of heating, the gas furnace is used

as a back-up.

Viessman Collectors

Sunvelope Collectors

Divicon

Controller

Expansion Tank

T T

Cooling TowerAbsorption Chiller

Expansion Tank

Drain

Expansion Tank

Drain

Chilled Water

Chilled Water Return

Water Return

Hot Water

Cooling Water

Cooling Water

T

T

T

T

T

T

T

T

To Pump (Supply)

To Pump (Supply)

Legend

Pressure Relief Valve

Manual Ball Valve

3-Way Solenoid Valve

T Thermocouple

Flow Meter

Pump

Viessman Water Tank

Sunvelope Water Tank

Check ValveOverflow Container

From Collector (Return)

From Collector (Return)

Heat Exchangers

The hot water from the solar panels is used to raise the temperature of

the refrigerant, causing it to evaporate.

Data on the system is

collected 24/7 every 5

minutes. Figure 7

shows various

temperatures over a

two day period. The

shaded regions

represent times when

the absorption chiller

was operating.

Fig. 7. Data collection from HVAC system

Fig. 8. Economizer

A custom economizer was built

for the HVAC system to provide

cooling, for times when the solar

collectors are not hot enough to

operate the absorption chiller.

The economizer draws in

outside air when the enthalpy

outside is lower than the

enthalpy inside.