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

ASME 2012 6th International Conference on Energy Sustainability, Parts A and B ◽

10.1115/es2012-91289 ◽

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.

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High Performance Passive Solar Heating System with Heat Pipe Energy Transfer

First E.C. Conference on Solar Heating ◽

10.1007/978-94-009-6508-9_65 ◽

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

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Heat Pipe Augmented Solar Heating System

ASME 2010 4th International Conference on Energy Sustainability, Volume 2 ◽

10.1115/es2010-90180 ◽

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%.

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EXPERIMENTAL AND THEORETICAL RESEARCH OF A HEAT-PIPE AUGMENTED PASSIVE SOLAR HEATING SYSTEM

Advances In Solar Energy Technology ◽

10.1016/b978-0-08-034315-0.50673-x ◽

1988 ◽

pp. 3647-3651

Author(s):

Klaus Meyer

Keyword(s):

Heat Pipe ◽

Heating System ◽

Solar Heating ◽

Theoretical Research ◽

Passive Solar

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High Performance Passive Solar Heating System with Heat Pipe Energy Transfer and Latent Heat Storage Modules

Solar Energy Applications to Dwellings ◽

10.1007/978-94-009-7924-6_17 ◽

1983 ◽

pp. 117-126 ◽

Cited By ~ 2

Author(s):

H. A. L. van Dijk

Keyword(s):

Energy Transfer ◽

Heat Pipe ◽

Latent Heat ◽

High Performance ◽

Heat Storage ◽

Heating System ◽

Solar Heating ◽

Latent Heat Storage ◽

Passive Solar

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A Reconfigureable Passive Solar Test Facility

ASME 2012 6th International Conference on Energy Sustainability, Parts A and B ◽

10.1115/es2012-91290 ◽

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.

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Solar Load Ratio Parameters for a Passive Solar Heat Pipe System

Volume 1: Advances in Solar Buildings and Conservation; Climate Control and the Environment; Alternate Fuels and Infrastructure; ARPA-E; Combined Energy Cycles, CHP, CCHP, and Smart Grids; Concentrating Solar Power; Economic, Environmental, and Policy Aspects of Alternate Energy; Geothermal Energy, Harvesting, Ocean Energy and Other Emerging Technologies; Hydrogen Energy Technologies; Low/Zero Emission Power Plants and Carbon Sequestration; Micro and Nano Technology Applications and Materials ◽

10.1115/es2015-49136 ◽

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.

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