Heat Pipe Augmented Solar Heating System

2010 ◽  
Author(s):  
Brian S. Robinson ◽  
Michael V. Albanese ◽  
Nick Chmielewski ◽  
Ellen G. Brehob ◽  
M. Keith Sharp
Keyword(s):  
Heat Pipe ◽  
Heating System ◽  
Solar Heating ◽  
System Component ◽  
Laboratory Model ◽  
Small Scale ◽  
Concrete Wall ◽  
Pipe System ◽  
Passive Solar ◽  
The One

The focus of this project is on simulation and testing of a novel passive solar heating system that utilizes the one-way heat transfer of heat pipes to significantly improve heating performance relative to conventional passive solar systems. A set of programmed thermal networks were used to simulate the performance of several conventional passive solar heating systems, including direct gain, concrete wall indirect gain and water wall indirect gain, and the heat pipe system. Simulations performed for four US locations representing a range of winter temperatures and available insolation exhibited higher performance for the heat pipe system, particularly in cold climates with low insolation. A small-scale laboratory model was constructed and tested under controlled conditions to confirm simulated system component performance and to test a range of component variations. Measured system efficiency was 85.1 ± 0.72%. A full-scale prototype was constructed, installed and instrumented. Results from a 21-day period in April show a prototype thermal efficiency range from 60–75% and an average of 66.2%; and a 30-day period in October and November ranges from 60–85% with an average of 73.9%. An opaque cover over the prototype, periodically installed to minimize unwanted gains during the cooling season, reduced overall gains by an average of 75%.

High Performance Passive Solar Heating System with Heat Pipe Energy Transfer

1984 ◽  
pp. 367-372
Author(s):  
M. H. de Wit ◽  
J. L. M. Hensen ◽  
H. A. L. van Dijk ◽  
G. J. van den Brink ◽  
E. van Galen
Keyword(s):  
Energy Transfer ◽  
Heat Pipe ◽  
High Performance ◽  
Heating System ◽  
Solar Heating ◽  
Passive Solar

Reducing Unwanted Gains During the Cooling Season From a Heat Pipe Augmented Passive Solar Heating System

2012 ◽  
Author(s):  
Brian S. Robinson ◽  
M. Keith Sharp
Keyword(s):  
Heat Transfer ◽  
Ambient Temperature ◽  
Heat Pipe ◽  
Control Strategies ◽  
Mechanical Valve ◽  
Heating System ◽  
Solar Heating ◽  
Weather Data ◽  
Beam Radiation ◽  
Passive Solar

The heat pipe augmented solar heating system significantly reduces heating loads relative to other conventional passive space heating systems [1–3]. Yet unwanted thermal gains during the cooling season from passive solar systems increase cooling loads and, in extreme cases, may even increase overall space conditioning loads relative to a nonsolar building. The objective of this study was to compare the effectiveness of several design modifications and control strategies for the heat pipe wall to reduce unwanted gains. MATLAB was used to simulate four different unwanted gains reduction mechanisms: 1. shading to block beam radiation from striking the collector, 2. an opaque cover to block all radiation from striking the collector, 3. a mechanical valve in the adiabatic section to eliminate convective heat transfer through the heat pipe into the room, and 4. switching the elevations of the evaporator and condenser sections of the heat pipe to provide heat transfer out of the room during the cooling season. For each mechanism, three different control strategies were evaluated: 1. Seasonal control, for which the prescribed mechanism is deployed at the beginning and removed at the end of the cooling season, 2. ambient temperature-based control, for which the mechanism is deployed if the forecast for the next hour (based on TMY3 weather data) is greater than 65°F, and 3. room temperature-based control, for which the mechanism is deployed if auxiliary cooling was required for the previous hour. For the seasonal strategy, the months for which the unwanted gains reduction mechanism should be deployed to minimize overall space conditioning loads were estimated with a season determination ratio (SD), defined as the monthly ratio of unwanted gains to heating load. Results suggested that SD may be a ‘universal’ parameter that can be applied across a range of climates for quick assessment of its optimal cooling season. With TMY3 data for Louisville, KY, the heat pipe system performed best with ambient temperature-based control. The mechanical valve was the best single mechanism. While in many cases the combination of the valve with a cover or shading produced slightly better performance than the mechanical valve alone, these additional reductions were small. Switching elevations of the evaporator and condenser sections produced little cooling, because of the low thermal emittance of the absorber and low thermal transmittance of the cover, and for the Louisville climate, small diurnal temperature swings during the summer.

Comparative Performance of Two Prototypes of a Passive Solar Heat Pipe System

2014 ◽  
Author(s):  
Brian S. Robinson ◽  
M. Keith Sharp
Keyword(s):  
Heat Pipe ◽  
Test Facility ◽  
Reverse Direction ◽  
Storage Tanks ◽  
New Model ◽  
Solar Heat ◽  
Pipe System ◽  
Evaporator Section ◽  
Passive Solar ◽  
New System

Thermal performance of an improved passive solar heat pipe system was directly compared to that of a previous prototype. Simulated and experimental results for the first prototype established baseline performance. Subsequently, potential improvements were simulated, and a second prototype was built and tested along side the first. The system uses heat pipes for high rates of heat transfer into the building, and limited losses in the reverse direction. The evaporator section of each heat pipe is attached to a glass-covered absorber on the outside of a south wall, and the slightly elevated condenser section is either immersed in water in a thermal storage tank or exposed to air in the room. Two-phase flow occurs in the heat pipe only when the evaporator is warmer than the condenser, creating a thermal diode effect. Computer simulations showed that system performance could be improved by using thicker insulation between the absorber and the storage tanks, and by switching from a copper to a rubber adiabatic section, which both reduced heat losses to ambient from the storage tanks. Early morning heating was improved by exposing one of five condensers directly to room air, which also improved overall system efficiency. A copper solar absorber soldered to the copper evaporator section improved heat conduction compared to the previous aluminum absorber bonded to the copper evaporator. Together these modifications improved simulated annual solar fraction by 20.8%. The new prototype incorporating these changes was tested along side the previous prototype in a two-room passive solar test facility during January through February of 2013. Temperatures were monitored with thermocouples at multiple locations throughout the systems, in each room and outdoors. Insolation was measured by four pyranometers attached to the building. Results showed that the design modifications implemented for the new model increased thermal gains to storage and to the room, and decreased thermal losses to ambient. The load-to-collector ratio for the experiments was 2.7 times lower than for the simulations, which decreased the potential for experimental improvements compared to the simulated improvements. However, average daily peak efficiency for the new system was 85.0%, compared to 80.7% for the previous system. Furthermore, the average storage temperature over the entire testing period for the new model was 13.4% higher than that of the previous model, while the average room temperature over the same period was 24.6% greater for the new system.

A Reconfigureable Passive Solar Test Facility

2012 ◽  
Author(s):  
Brian S. Robinson ◽  
M. Keith Sharp
Keyword(s):  
Heat Pipe ◽  
Side Wall ◽  
Building Envelope ◽  
Test Facility ◽  
Weather Data ◽  
The South ◽  
Original Design ◽  
Pipe System ◽  
South Wall ◽  
Passive Solar

A 12′ by 24′ passive solar test building has been constructed on the campus of the University of Louisville. The building envelope is comprised of structural insulated panels (SIPs), 12″ thick, (R-value of 45 ft2F/Btu) for the floor and walls and 16″ (R-63) for the roof. The building is divided into two symmetrical rooms with a 12″ SIPs wall separating the rooms. All joints between panels are caulked to reduce infiltration. Each room contains one window (R-9) on the north side wall, and two windows (also R-9) facing south for ventilation and daylighting, but which will also provide some direct gain heating. The south wall of each room features an opening that will accommodate a passive solar heating system so that performance of two systems can be compared side-by-side. The overhang above the south openings is purposely left short to accommodate an awning to provide adjustable shading. The calculated loss coefficient (UA) for each room of the building is 6.07 W/K. Each room is also equipped with a data acquisition system consisting on an SCXI 1600 16 bit digitizer and an SCXI 1102B isolation amplifier with an SCXI 1303 thermocouple module. Pyranometers are placed on the south wall and the clerestory wall to measure insolation on the solar apertures. For initial tests, one room is equipped with an original heat pipe system previously tested in another building, while the other is equipped with a modified heat pipe system. Changes to the modified system include copper absorbers versus aluminum, an adiabatic section constructed of considerably less thermally-conductive DPM rubber than the copper used for the original design, and one of the five condenser sections of the heat pipes is exposed directly to the room air to provide early-morning heating. Experimental results will be compared to simulations with as-built building characteristics and actual weather data. Previous simulations with a load to collector ratio of 10 W/m2K, a defined room comfort temperature range between 65°F to 75°F, and TMY3 weather data for Louisville, KY, showed that the modified heat pipe wall design improves annual solar fraction by 16% relative to the original design.

Solar Load Ratio Parameters for a Passive Solar Heat Pipe System

2015 ◽  
Author(s):  
Logan S. Poteat ◽  
M. Keith Sharp
Keyword(s):  
Heat Pipe ◽  
Load Ratio ◽  
Building Design ◽  
Weather Data ◽  
Prediction Algorithm ◽  
Solar Heat ◽  
Pipe System ◽  
Thermal Network ◽  
Pipe Systems ◽  
Passive Solar

The Solar Load Ratio (SLR) method is a performance prediction algorithm for passive solar space heating systems developed at Los Alamos National Laboratory. Based on curve fits of detailed thermal simulations of buildings, the algorithm provides fast estimation of monthly solar savings fraction for direct gain, indirect gain (water wall and concrete wall) and sunspace systems of a range of designs. Parameters are not available for passive solar heat pipe systems, which are of the isolated gain type. While modern computers have increased the speed with which detailed simulations can be performed, the quick estimates generated by the SLR method are still useful for early building design comparisons and for educational purposes. With this in mind, the objective of this project was to develop SLR predictions for heat pipe systems, which use heat pipes for one-way transport of heat into the building. A previous thermal network was used to simulate the heat pipe system with Typical Meteorological Year (TMY3) weather data for 13 locations across the US, representing ranges of winter temperature and available sunshine. A range of (nonsolar) load-to-collector ratio LCR = 1–15 W/m2K was tested for each location. The thermal network, along with TMY3 data, provided monthly-average-daily absorbed solar radiation and building load to calculate SLR. Losses from the solar aperture in a heat pipe system are very low compared to conventional passive solar systems, thus the load-to-collector ratio of the solar aperture was neglected in these preliminary calculations. Likewise, nighttime insulation is unnecessary for a heat pipe system, and was not considered. An optimization routine was used to determine an exponential fit (the heart of the SLR method) to simulated monthly solar savings fraction (SSF) across all locations and LCR values. Accuracy of SSF predicted by SLR compared to the thermal network results was evaluated. The largest errors (up to 50%) occurred for months with small heating loads (< 80 K days), which inflated SSF. Limiting the optimization to the heating season (October to March), reduced the error in SSF to an average of 4.24% and a standard deviation of 5.87%. These results expand the applications of the SLR method to heat pipe systems, and allow building designers to use this method to estimate the thermal benefits of heat pipe systems along with conventional direct gain, indirect gain and sunspace systems.

Performance of a passive solar heating system in multi-span Moroccan greenhouse

2020 ◽  
pp. 211-218
Author(s):  
L. Gourdo ◽  
H. Fatnassi ◽  
K. Achgar ◽  
A. Chraibi ◽  
B. Ouaddich ◽  
...  
Keyword(s):  
Heating System ◽  
Solar Heating ◽  
Passive Solar
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