Waste Heat Recovery from PV Panels FINAL PRESENTATION

Background Started from Solar Decathlon HU/ODU Project SunDrum’s role as a heat recovery unit for this project Chris(first 2 bullets)Hello everyone! We are the PV Waste Heat Group and I am sure you have probably seen our project sitting out behind Kaufmann but might not know what it is. We actually inherited this project from a joint project with Hampton University and ODU for a Solar Decathlon to build a “green home” that could run off of solar energy. The project was unable to be completed and as such, we have now inherited the project to finish testing and analysis that was never able to be completed. The basic premise of our project relies on pulling waste heat from solar panels through the use of heat exchangers so as to provide hot water for domestic uses. As a result of pulling heat from the panels, we also lower the temperature of the panels thereby increasing the overall efficiency of the panels given that the lower a panels temperature gets, the closer the panel gets to working at its maximum efficiency. To gather tha appropriate data to analyze the overall effects of our heat exchangers, we built a rig to hold all the necessary components. Around :55-1:05

Testing Rig’s Function Water, which is pumped through the heat recovery units, carries the waste heat produced by the PV panels during system operation to a hot water tank. The PV panels capture the sun’s energy, which is dissipated into a pair of variable resistance heatsinks. Heat recovery units (SunDrum) are attached to the back of 3 panels (6 total). Chris

Experimental Process Main Goal: To monitor and quantify the removal and capture of waste heat from back of PV panels Variables which will be measured: Primary - Temperature rise of water in tank and of the fluid flow through closed loop. Secondary - Data as provided by Tigo (Power production) and panel surface temperature (infrared laser thermometer gun) Mark

Junction boxes (resistors & breakers) Panels with SunDrum Junction boxes (resistors & breakers) Pump station Chris MMU Hot water tank

Plumbing/Water System Installation of flexible piping between Sundrums Connection of pump to closed loop system Installation of hot water tank as heat dump System filled and pressurized. Taylor Between 1-1:30

TIGO-Data Acquisition Three pieces of Tigo equipment Maximizer Module Management Unit (MMU) Gateway Alex

**Stay on schematic page during transition from Alex to Hal before transitioning into next slide**

Electrical System Design: Variable resistance heatsinks provided load for panels. Resistors/breakers inside weather rated enclosures, mounted to lower wooden structure Clamp affixed to a grounded pipe acted as the main ground connection. Hal-time was _____ **Stay on schematic page before transitioning into this slide** The electrical system was designed with the help of the electronics technician, shown here.The DC wiring from the panels are connected to a double pole circuit breaker (lower box, for safely separating the panels from the resistors). From the breakers, the wiring is hooked to a variable resistance heat sink. These heat sinks acted as the resistance for the circuit, allowing the panels to being producing power. (upper box). The breakers and the resistors are both mounted in NEMA rated enclosures. The upper box which contains the resistors is vented; the heat sinks’ thermal resistance was substantial enough that venting for cooling air flow was required. The enclosures are mounted to the base structure (LEFT). The system is grounded to a large pipe using a pipe clamp in the loading bay of Kaufman. (RIGHT) Once the junction boxes were mounted and electrical connections were complete, we began testing >>>>>>next slide (TRANSITION)

Results The graph to the right shows the three measured temperatures throughout a day with favorable conditions. It is worth noting that pump was left running overnight, which cycled that heat which recovered by the SunDrums back out of the tank. Hal The graph shown here is a plot of the send/return(blue/orange) pump temperatures, as well as the tank temperatures (gray), on an hourly basis for the best testing day we had, April 10th. The tank temperature started at roughly 45 degrees, and increased in a fairly constant fashion (5 degrees per half hour) until the shade covered the panels, around 4PM. The final tank temperature was just over 100 degrees. Note that the pump was left running in between sessions. After multiple sessions with similar trends, we decided to (per recommendation of our advisor) turn the pump off in between testing sessions, in an attempt to raise the initial tank temperature >>>>>>>>>>next slide

Results The graph to the right shows the three measured temperatures throughout a day with favorable conditions. It is worth noting that pump was turned off overnight, which had a profound effect on the amount of retained heat in the tank. Taylor

Results The graph to the right shows the three measured temperatures throughout a 36 hour period. Power increase between the panels with SunDrum and those without was roughly 12%. Rainy day End of day Coldest Night Taylor

Conclusions After observation of the tank temperature at the end of each testing session, it was determined that 3 units alone would not be sufficient to provide enough heat for domestic hot water usage. Temperature to safely kill off formation of Legionella bacteria, source of Legionnaire’s disease, is 140F. Final tank temperature on clear days was on average ~104F (when pump was running) and 122F (when pump was off). Resistance limitations-The resistors which were in place were found to be operating at a higher resistance (~130 Ω) than what was read from the specification sheet (47 Ω). This limited power output, and subsequently, heat removal potential. trent

Modifications To increase power output More suitable resistors To increase maximum temperature of hot water tank Surface color of SunDrum Higher current PV Panels To increase rate of heat transfer Plumbing connections in parallel Keira

Variable Resistors Resistor temperature increased up to 330 degrees F ↑ resistor temperature causes ↓ resistance Bosch PV Panel maximum current ~ 8 amps By equation P=RI^2, ↓ resistance causes ↓ power output Keira:

Surface Color of SunDrum Units Maximum achieved temperature of hot water was 122°F. Goal temperature for domestic application is 140°F Maximum temperature of hot water tank ~ temperature of the back of PV panels Limiting factors are PV panel and SunDrum surface temperatures Increase temperature by maximizing absorption of solar radiation with matte black surface Keira The first is modifying the insulation. SunDrum provides ½” rigid board insulation which does not cover the entire surface area of the panel as shown in the image to the left. The insulation can be modified both by increasing the surface area covered by the insulation and by introducing different forms of insulation in order to reduce heat loss to the ambient. The second proposed modification is altering the semi reflective silver surface of the SunDrum as seen in the image on the right, to a matte black surface in order to maximize absorption of solar radiation, therefore increasing the amount of heat that can be recovered. That summarizes our plans for testing and our proposed modifications.

Gantt Chart

Questions?