• Journal of the Korean Solar Energy Society
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• v.31 no.5
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• pp.140-145
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• 2011

In this study, the performance and behavior of solar heating system according to the system control scheme, variable flow control (proportional control) and constant flow control (on-off control) was carried out by experiment. The on-off control is used generally for solar thermal system by now. But the proportional control is used for the solar district heating system which is supplied the higher temperature of water than that of desired. The proportional control logic that pump speed is varied in an attempt to maintain a specified outlet temperature of solar heating system was developed and tested for the use widely for the small and medium solar thermal system. The results are as following. First, the proportional controller which is made here could be adopted the characteristics for setting temperature control. Second, the proportional control is better than the on-off control in the side of the performance of thermal stratification in storage tank. Third, the operating energy(electricity consumption by pump) of solar thermal system can be saved more than 60% using the proportional control comparing to the on-off control.

• Journal of the Korean Solar Energy Society
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• v.27 no.3
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• pp.45-54
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• 2007

For a conventional natural-circulation type solar water heater, the pressure head is limited by the height between the storage tank and hot water tap. Therefore, it is difficult to provide sufficient hot water flow rate for general usage. This study deals with a design modification of the storage tank to utilize the tap-water pressure to increase hot-water supply Based on fluid dynamic and heat transfer theories, a series of modeling and simulation is conducted to achieve practical design requirements. An experimental setup is built and tested and the results are compared with theoretical simulation model. The storage tank capacity is 240 l and the outer diameter of piping was 15 mm. Number of tube turns tested are 5, 10, and 15. Starting with initial storage tank temperature of $80^{\circ}C$, the temperature variation of the supply hot water is investigated against time, while maintaining minimum flow rate of 10 1/min. Typical results show that the hot water supply of minimum $30^{\circ}C$ can be maintained for 34 min with tap-water supply pressure of 2.5 atm, The relative errors between modeling and experiments coincide well within 10% in most cases.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.564-569
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• 2007

This study describes thermal performance of solar cooling and hot water for demonstration system with ETSC(Evacuated tubular solar collector) installed at Seo-gu art center of Kwangju. For demonstration study, a reading room with about 350㎡ was heated and cooled with the solar system. The system was consisted of ETSCs, storage tank, hot water supply tank, subsidiary boiler, subsidiary tank, absorption chiller, chiller storage tank, and cooling tower. The results of the experimental study indicated that the total solar energy gain as daily performance on a sunny day (August 25, 2007) with total daily radiation of $606\;W/m^2$ was 671 kWh, the collecting efficiency of 55%. In the case of supplies to heat source more than $83^{\circ}C$, cooling time operated by solar was driven 8.8 hours, cooling energy generated by solar system was 179 kWh and the solar cooling fraction was 79.2%, and hot water supplied with surplus heat source by the solar system was 201 kWh.

• 한국태양에너지학회:학술대회논문집
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• 2008.11a
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• pp.141-146
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• 2008

For the efficient use of thermal energy and its related equipments, optimal energy in view of quality and quantity should be timely provided. The core of thermal energy storage technology deals with an energy efficiency for effective energy storage and supply. The relative importance of thermal energy storage technology has been underestimated so far, and the specific projects on this filed have been performed intermittently. For the efficient and systematic approach of the energy supply system projects on thermal energy storage technology, we conduct the survey on the current status of this field. Firstly, classify into the thermal energy storage and describing the recent research for each system. The necessity and importance of thermal energy storage technology is identified through this study. It reveals that the thermal energy storage is the mandatory technology to solve the difference of supply and demand in thermal loads. It would greatly contribute to the combined heat and power(CHP) system. The urgent technologies for the commercial value and the core technologies for the CHP system are classified with this study.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.688-692
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• 2007

Solar thermal power generation allows additional benefits of cheap thermal storage and easy hybridization with other fossil fuel-driven power generation. KIER has been performing the project for solar thermal chemical reaction hybrid power generation. The project is to build and operate the first solar thermal chemical reaction hybrid power generation system in Korea. For concentrating solar thermal energy $m^2$ dish type concentrator was adapted and a heliostat is installed for reflecting horizontal insolation to the dish concentrator. At the moment building the dish concentrator including mirror and heliostat with sun tracking system was completed and it's performance are being closely evaluated. This paper will introduce some detailed designs and construction procedures which we have experienced so far.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.190-193
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• 2008

The heat transfer characteristics of molten salt storage system for the solar thermal power generation were investigated. Temperature profiles and the heat transfer coefficients during the storage and discharge stage were obtained with the steam as the heat transfer fluid. Two kinds of inorganic salt were employed as the storage materials and coil type of heat exchanger were installed in both tanks to provide the heat transfer surfaces during the storage and discharge stage. The effects of steam flow rates, flow direction of steam in the storage tank and the initial temperature of storage and discharge tank on the heat transfer were tested.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.105-110
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• 2006

Several types of solar water heating system were analyzed in characteristics and proper systems were proposed under Korean climates. In particular, the forced circulation type with a spiral-jacketed storage tank has a potential to be used widely in a small and a part of middle systems when the stratification of the storage tank can be enhanced by a precise design.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.563-566
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• 2006

An investigation has been carried for the thermal characteristics of the seasonal storage installation in Cheju. It features the solar collector area of $340m^2$ and the storage capacity of $600m^3$. Four different types of solar collector systems are compared for their performance of collecting solar energy throughout the year. Of these, two are made of tubular shaped vacuum collectors and the others are flat plate collectors. Results indicate that each system could play an important role in exploiting solar energy depending on the temperature range in its operation. Especially, the vacuum collectors outperformed the others when the inlet temperatures of the collector loop were raised beyond $40m^2$. This became more conspicuous as the return temperatures from the storage tank rose reflecting the seasonal variation. Due to the large heat capacity of the storage tank, temperature changes were rather small compared to those in the collecting loop regardless of seasonal fluctuations.

• Journal of the Korean Solar Energy Society
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• v.28 no.1
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• pp.75-81
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• 2008

Thermal performance of passive solar Trombe wall system which is applied on the south wall of KIER Zero energy Solar House has been monitored for 6 months of heating season. Based upon the long-term measurement results, extensive statistical analysis was conducted to investigate temperature profiler and heat flow pattern in Trombe wall system under actual operating condition. Heat flow characteristics depending on the time variation of day and month was clearly revealed. Heat gain and loss on the inner surface of the Trombe wall was calculated base upon measured temperature data. Those results would be utilized to improve the efficiency of new type solar storage wall system.

• Journal of the Korean Solar Energy Society
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• v.33 no.6
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• pp.12-18
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• 2013

Domestic solar hot water system can be divided into a passive type and an active type. In a passive type the storage tank is horizontally mounted immediately above the solar collectors. No pumping is required as the hot water naturally rises into the storage tank from the collectors through thermo-siphon flow. While, in an active type the storage tank is ground- or floor-mounted and is below the level of the collectors; a circulating pump moves water or heat transfer fluid between the storage tank and the collectors. We installed two types solar hot water systems consisting of the same storage tank and collectors at the same place, and were measured and compared typical operating characteristics under the same external conditions. In particular, the daily system performance was presented through the stirring test after the sunset. The results show that the amount of solar radiation obtained for an active type were less than a passive type on a cloudy day, because the operation of the circulation pump stops frequently took place on that day. However, on a sunny day, depending on the stable operation of the circulation pump, the amount of solar radiation obtained for an active type were increased than a passive type.