Hybrid photovoltaic/solar thermal heat pump (PV/T+HP) system


Thanks to Albert Nunez of http://www.capitalsungroup.com/ for allowing me to post this project overview, it won the AEE innovative project of the year by unanimous decision from among 400 international entries submitted.
Maurice Duteau
General Manager
Temco Controls

Albert Nunez writes:
This hybrid PV/T HP project, designed and built by Capital Sun Group, maximizes roof-mounted solar energy collection utilizing a sandwiched dual collector system. The array combines high-performance SunPower® photovoltaic panels for generating electricity with SunDrum® Solar thermal panels mounted on their PV’s rear surfaces to collect heat. The thermal component is a closed glycol loop acting as the source for a heat pump that amplifies the collected energy to heat the home, domestic hot water and pool/storage water. Summer cooling rejects waste heat to the night sky via the solar array. A closed loop circulates propylene glycol to the source side of a water-to-water heat pump whose load side heats the home via a water-to-air coil mounted above the legacy 92% efficient gas furnace retained as backup.

Using three-way diverting valves, this load loop also delivers heat to the swimming pool, which is insulated in the winter months to store solar heat for nighttime use. Solar thermal energy collection is recorded on revenue grade Btu meters, allowing the client to participate in the Washington, DC Thermal SREC market. Further, solar power harvested is recorded on a revenue grade WattNode® meter for electricity SREC accounting. Cooling the home while heating the pool and domestic hot water, the system achieves a high TOTAL COP. Water heating gas consumption is minimal in the heating and cooling seasons. The fully instrumented monitoring system by Net Zero Meter provides real-time and historical summaries viewable online.

Since the system’s commissioning in January 2016 to September 2017, the Enser Morris Hybrid PV/T HP System has provided 84.3% of the domestic water heating load, 86.1% of the space heating load, over 95% of the space cooling load, 100% of the pool heating load, and approximately 75.3% of the total electrical power consumed by the project. The clients are continuing to strive for a “Net Zero Home” by implementing further energy conservation measures (ECMs) to minimize their carbon footprint.


Albert.Nunez[at]CapitalSunGroup[dot]com Phone: 202-270-5000

Michael Intrieri mintrieri[at]SunDrumSolar[dot]com 978.562.5152

George.Jalbert[at]NetZeroMeter[dot]com 978.697.5227

System Component Details:
 46 SunPower photovoltaic panels – model SPR-X21-250-BLK (250Wp)
 Tigo Optimizers for panels level monitoring and rapid shutdown capability
 2 SunPower - SMA-America Sunny Boy SB500TL-US String Inverters
 42 SunDrum ® Solar thermal panels - Model SDM100-30 (480Wp)
 SunDrum ® Solar HarvestHPTM (WaterFurnace) Envision Model: NSW-040
 4-ton Reversible with Desuperheater and Intelistart
 Grundfos Magna3 Smart Pump on Solar Glycol Loop
 Grundfos Stainless Steel Alpha Pump on Desuperheating Loop
 Grundfos Cast Iron Alpha Pumps on Load and Direct Solar DHW Preheat Loops
 Pentair IntelliFlo Variable Speed Pool Pump with Digital Time Clock | 3HP Max
 Belimo Three-way Motorized Diverting Valves
 Goldline- Jandy Three-way Pool Water Diverting Valve
 80 Gallon Dual Heat Exchanger Kingspan Stainless Steel Solar Storage Tank
 K3N Spirec Stainless Steel Heat Exchanger (Pool Water/Glycol Loop)
 Magic Aire 4-ton Water-to-Air Coil
 EcoBee3 Smart Thermostat with Remote Sensor
 Temco Controls T3-Big Brother Direct Digital Control (DDC) System
 1 Resol DeltSOL MX Solar Controller with 2 Expansion Modules (EM) & Data Logger (DL3)
 Solar-Cell SunblanketTM (Double Layer in Winter) with Winter Cover Over Top
 Net Energy Meter Data Acquisition System
 3 WattNode Revenue Grade Watt Meters
 4 Istec Revenue Grade Btu Meters
 1 Temco Controls 1” Flow Meter
 1 Davis Weather Station

Maurice writes: The following are my own excerpts from Mr. Nunez’s presentation:

One important principle this system uses is to cool the PV solar panels to improve their efficiency. This is done by running cool glycol/water solution from the pool heat exchanger through a novel SunDrum® Solar flat plate collector water heating system that is sandwiched behind the PV solar panels. The waste heat gathered by the solar hot water heating system is used to heat the pool water, as well as the home via a hot water coil and the domestic hot water via a solar heat-exchanger preheat tank. In the summer months the home heat is used to heat the pool and waste heat can be rejected to the night sky via the SunDrum® Solar array.

The system has many modes of operation which are coordinated by programs running on the T3-BB controller. Several valves route the water to the solar panels, the pool and the water coupled heat pump depending on the heating and cooling loads of the house and pool.

Here is another Net Zero Meter Data Acquisition System (DAQ) overview screen that shows a mechanical diagram of the system.

Here is a look at the T3-BB and a few of the many hardware components that make up this complex system.

And here is Albert accepting his AEE award. Congratulations to Albert and the team.

This project pushed us at Temco Controls to make sure our product was up to the task, the program tested the T3-BB to the limits. One of the things we ran into recently is running out of program space, as the programming became more complex to include more energy conservation measures the controller was running low on resources. We have since bumped up the space for user programs by a factor of three which gives Albert and his team room to grow.