Storage Water Heaters Research Articles

Numerical Simulation, Design, and Construction of a Double Glazed Compound Parabolic Concentrators-Type Integrated Collector Storage Water Heater

The numerical simulation, design, and construction of a double glazed integrated collector storage (ICS) with compound parabolic concentrators (CPC) reflectors are presented. The design of the double glazing is optimized by means of numerical simulations under Tunisian climatic conditions. The numerical program used for the simulation consists on the transient resolution of the balance energy equations of each component of the solar water heater. Different proposed models of a double glazing are studied and compared with a reference case of a single glass ICS model. The simulation results have shown that the use of double glazing with argon layer and low-e coated lower glass instead of one glass cover significantly improves the thermal behavior of the ICS heater and visibly reduces its thermal losses during night. Taking into account these numerical results, a double-glazing ICS prototype-collector is constructed. The details of the construction, geometry, optical properties, and dimensions of the prototype are presented.

Experimental Investigation on a Solar-powered Absorption Radiant Cooling System

Abstract Solar cooling has been proved to be technically feasible. It is particularly an attractive application for solar energy, because of the near coincidence of peak cooling loads with the available solar power. Currently, most of the solar cooling systems commonly used are the hot water driven lithium bromide absorption chillers. Solar absorption cooling systems are available from various reports, in large capacities up to several hundred kilowatts. In this paper, a minitype solar absorption cooling system was designed and installed in Shanghai Jiao tong University. The system mainly contains 96 m2 solar collector arrays, one absorption chiller with the rated cooling capacity of 8 kW, and a heat storage water storage tank of 3 m3 in volume. The chilled water can be delivered either into fan coils or into radiant cooling panels which are installed to satisfy the indoor thermal environment of the test room. As for the fan coil cooling mode, it was found that the average cooling output reached 3.62 kW during 8 h operation under typical weather condition of Shanghai. With regard to radiant cooling mode, an individual fresh air unit was installed for the purpose of preventing the cooling panels from condensation. Compared with the experimental results of the fan coil cooling mode, the average cooling output of the radiant cooling mode reached 4.47 kW, which increased by 23.5%. Furthermore, the PMV inside the test room was between -0.5 and 0.5, which showed great advantage in meeting the indoor thermal comfort.

Numerical calculations of heat engineering parameters of a solar greenhouse dryer

The results of numerical simulation to determine the optimum volume of a thermal storage water heater in a solar greenhouse dryer are presented. A CAD (computer-aided design) model is created for the given installation by simulating the heat transfer processes with the aid of the Solid Works Flow Simulation software. The given CAD model consists of a concrete foundation and a steel frame in which translucent coatings made from two-layer polycarbonate sheets 6 mm in thickness with an air gap between the two layers are attached. The north wall is made of bricks with size and thickness of 2 × 4 m2 and 0.4 m, respectively. The front surface has an angle of inclination 39.53° with respect to the horizontal surface for the maximum incidence of solar radiation to its surface. All the geometrical dimensions of the solar greenhouse dryer were selected on the basis of the allocated platform for the solar drying installation 3 × 4 m2 in size. It is shown that the optimum volume of the heat storage tank for the present installation is 500 L.

Development of a New Energy-Saving Pipe-Framed Greenhouse

We summarize the basic techniques used to save energy in a greenhouse and discuss the development of a new energy-saving pipe-framed greenhouse, similar to the type used on most small-scale farms in Japan. To enhance the thermal insulation performance of a pipe-framed greenhouse, a multi-layered thermal curtain was installed. As a result of our experiments, both the heating load and the heating oil consumption in the greenhouse with a multi-layered thermal curtain (M-house) were approximately 40% lower than those in the control greenhouse with a conventional thermal cover (C-house). Furthermore, the heating oil consumption was also reduced by approximately 60% in the M-house equipped with water heat storage, which stored solar energy in daytime and released heat to the greenhouse at night. This multi-layered thermal curtain is expected to gain recognition as the most effective energysaving material available and immediate widespread use nationwide is expected. Another experiment was performed concerning the structural reinforcement of pipe-framed greenhouses. Pipe-framed greenhouses are usually constructed with single-arch pipes in Japan and there has been a recent increase in greenhouses collapsing due to strong winds. Accordingly, techniques to reinforce the structure of pipe-framed greenhouses were also developed. Discipline: Horticulture Additional key words: heating load, heat transmission, multi-layered thermal curtain *Corresponding author: e-mail hirokik@affrc.go.jp Received 31 March 2014; accepted 24 December 2014. Introduction In Japan, greenhouses used for protected horticulture take up an area of approximately 50,000 ha, about 40% are equipped with a heating system and more than 90% depend on fossil fuel. In Japan, protected horticulture is responsible for 45% of all carbon dioxide emissions (about 611 million tons) derived from fossil fuels used for agriculture, forestry and fisheries (Hayashi 2008). Most fossil fuels are used in protected horticulture for heating oil and the amount of fuel consumed for this purpose increased about 2.2 times from 1990 to 2005. Energy costs have also been steadily increasing, which has become an important factor influencing the management of farms. Accordingly, it has become necessary to develop energy-saving techniques for protected horticulture. In Japan, approximately 80% of all greenhouses are high-tunnel and high tunnel-like greenhouses; these are referred to as pipe-framed greenhouses, where the frames are constructed from steel pipes. The high tunnel, where sidewalls are not round like a hooped house, has no electrical service, automated ventilation or heating system (Lambert 2009). This review focuses on pipe-framed greenhouses in Japan with a heating system and other environmental control equipment. Basic energy-saving techniques for greenhouses have been classified into three groups: 1) reducing heating load, 2) introducing a high-efficiency heating system and 3) temperature management, namely, varying night temperature control, local air heating, the usage of cultivars for low-temperature tolerance and so on (Hayashi 2008). These techniques are usually used in combination. The key energy-saving technique in greenhouses involves reducing heating load or loss by installing a fixed or movable covering, an air-inflated covering, etc. (Naito 1981). Overnight, heat loss from greenhouses occurs due to overall heat transmission through coverings and structures. It is also caused by air infiltration and heat flux of the inside-air to the soil, although this is reversed in some cases. Heat transmission accounts for a large part of the total heat loss from a greenhouse, followed by heat transfer due to air

Comparison of actual water evaporation and pan evaporation in summer over the Lake Poyang, China

水面蒸发是湖泊水量平衡要素的重要组成部分.基于传统蒸发皿观测蒸发不能代表实际水面蒸发,而实际水面蒸发特征仍不清楚.本研究基于涡度相关系统观测的鄱阳湖水体实际水面蒸发过程,在小时和日尺度分析了水面蒸发的变化规律及其主要影响因子,并与蒸发皿蒸发进行比较.研究表明,实际水面蒸发日变化波动剧烈,变化范围在0~0.4mm/h之间.水面蒸发的日变化特征主要受风速的影响.鄱阳湖8月份日水面蒸发量与蒸发皿蒸发量在总体趋势上具有很好的一致性.8月份平均日水面蒸发速率(5.90mm/d)比蒸发皿蒸发速率(5.65mm/d)高4.6%.水面日蒸发量与蒸发皿蒸发量的比值在8月上、中、下旬平均值分别为1.24、1.00、0.92,呈现下降的趋势.鄱阳湖夏季水面日蒸发量与风速和相对湿度相关性显著,而蒸发皿蒸发与净辐射、气温、饱和水汽压差和相对湿度均呈显著相关.这是由于蒸发皿水体容积小,与湖泊相比其水体热存储能力小,因此更容易受到环境因子的影响.;Evaporation is an important factor in water balance of lakes. The evaporation pan is a traditional method to observe water evaporation, while it cannot represent actual water evaporation. So the characters of actual water evaporation are still unclear. In this study, the actual water evaporation was measured by an eddy covariance system over the Lake Poyang in August of 2013. We analyze the diurnal and monthly variations of water evaporation and its main influencing factors, and compare it with pan evaporation measured at Tangyin station. The results show that the water evaporation has strong turbulence in diurnal variations in the range of 0-0.4mm/h. The diurnal variation of water evaporation is mainly controlled by the wind speed. The daily water evaporation has similar trend with daily pan evaporation in August over the Lake Poyang. The average water evaporation in August is 5.90mm/d, which is higher than 4.6% for average pan evaporation(5.65mm/d). The ratio of water evaporation to pan evaporation in August shows decreasing trend, and the ten-day average ration was 1.24, 1.00, 0.92, respectively. The daily water evaporation in August has good relationship with wind speed and relative humidity, and pan evaporation was significantly related to net radiation, air temperature, the saturation vapor pressure deficit and relative humidity. This is due to evaporation pan has small volume and weak water heat storage capacity comparing with the lake, thus it easily affected by environmental factors.

Experimental performance analysis of a solar assisted ground source heat pump system under different heating operation modes

This paper presents an experimental study on the influence of operation modes on the heating performance of a solar assisted ground source heat pump system (SAGSHPS). Through experiments conducted in January, the characteristics of the SAGSHPS were investigated under different heating operation modes. The results indicate that the solar thermal could be used to accelerate the soil recovery when the heat pump unit is turned off, but the duration of solar use to recharge boreholes should be optimized according to the water temperature in the solar heat storage water tank to avoid unnecessary power consumption of the circulation pump. In addition, the solar heat storage water tank is beneficial for the stable operation of the SAGSHPS. The volumetric flow rate in the water tank has a significant impact on the electricity consumption of the SAGSHPS. From comprehensive analysis of the integral effect of the SAGSHPS under different modes, the mode in which the water tank is connected with the ground heat exchangers (GHES) in series is the recommended mode for the SAGSHPS in the coldest month in Dalian.

Research and Development of New Efficient Instantaneous Hot Water Heaters

With the improvement of living standards, people's lives have become increasingly dependent on water heater facility. Fast electric water heater is environmental, economic, more convenient than storage water heaters. Compared with gas water heaters, it’s more safe and energy-efficient . This article will introduce a safe and efficient hot-water heaters, through reasonable optimizing its structure so that it can heat the water in the 3s, but by deepening the circuit schematic to ensure the safety function.

Temporal and spatial variations in radiation and energy balance across a large freshwater lake in China

The surface radiation and energy exchange processes are important drivers of lake evaporation and the associated hydrological cycle. In this paper, we investigated the temporal and spatial variations in evaporation and the associated radiation and energy fluxes across Lake Taihu, China with an eddy covariance mesonet consisting of three lake sites and one land site. The results indicate that on the diurnal scale, water heat storage showed a similar behavior to net radiation with comparable magnitudes and fueled the substantial nighttime evaporation (48% of annual evaporation). Unlike boreal deep lakes, the monthly mean sensible and latent heat flux was tightly coupled with seasonal variations in net radiation at this large (size 2400km2), subtropical (30.9–31.6°N) shallow (mean depth 1.9m) Lake Taihu. On the monthly to annual scales, the radiation and energy fluxes showed little spatial variations across the lake, indicating a lack of sensitivity to wind speed, water depth, water quality and the presence of submerged macrophytes. The annual mean Bowen ratio (0.12–0.13) of the lake was lower than those found in the literature for subtropical and northern lakes and also much lower than that observed at the adjacent land site (0.58). The experimental data were used to evaluate the performance of 19 lake evaporation models of varying complexities.

First Experience in Vacuum Insulated Hot Water Storage with 100 m3

This article presents the results of an experiment that aimed to determine the effective thermal conductivity of the first 100 m3 vacuum-insulated hot water heat storage. For this, the store was filled with 82°C hot water. Thereafter, the temperature decrease was measured over 31 days. A U-value of 0.36W/(m2 K) was calculated using the energy balance model of Raab [1]. This article also presents some pictures of the construction of the heat store.

Development of Innovative Heating and Cooling Systems Using Renewable Energy Sources for Non-Residential Buildings

Industrial and commercial areas are synonymous with high energy consumption, both for heating/cooling and electric power requirements, which are in general associated to a massive use of fossil fuels producing consequent greenhouse gas emissions. Two pilot systems, co-funded by the Italian Ministry for the Environment, have been created to upgrade the heating/cooling systems of two existing buildings on the largest industrial estate in Umbria, Italy. The upgrade was specifically designed to improve the system efficiency and to cover the overall energy which needs with renewable energy resources. In both cases a solar photovoltaic plant provides the required electric power. The first system features a geothermal heat pump with an innovative layout: a heat-storage water tank, buried just below ground level, allows a significant reduction of the geothermal unit size, hence requiring fewer and/or shorter boreholes (up to 60%–70%). In the other system a biomass boiler is coupled with an absorption chiller machine, controlling the indoor air temperature in both summer and winter. In this case, lower electricity consumption, if compared to an electric compression chiller, is obtained. The first results of the monitoring of summer cooling are presented and an evaluation of the performance of the two pilot systems is given.

The Performance of Different Sand Beds Solar Stills

The amount of distillate water from a solar still depends on different parameters. The heat storage bed and water depth are the most effective parameters. In this work, different sand beds solar stills have been studied experimentally. The influences of sandy bed height (0.01, 0.02, 0.03, and 0.05 m), type of sand (black and yellow), and the water height above the sandy bed level (0.0, 0.01, 0.02, and 0.03 m) on the solar still performance have been investigated. The performance of developed sand beds stills was compared with the conventional solar still. Results showed that the heat storage bed (sandy layer) enhances the solar still productivity. The maximum increase in daily productivity of sandy solar still was achieved at sand beds height of 0.01 m and zero height of saline water above the sand beds level as compared with conventional still. A theoretical analysis has also been carried out, in which the results coincided with experimental results.

The Experimental Study of Water Storage Performance on Small Heat-Pump Energy Storage Air-Conditioner

Based on the performance of energy storage air conditioning system, a small heat pump water heat storage air conditioner was designed with some experiments in winter running. The experiments show that the heat storage system can improve inlet temperature of the refrigerating compressor effectively when proceeding heating mode, and the outlet temperature is also higher relatively; In the low-temperature heating condition, the maximum heating capacity can up to more than the rated heating capacity and the defrosting performance is better too; But the heat storage capacity of the system is quite limited for the thermal storage material is water.

Financial measures Serbia should offer for solar water heating systems

Hot water consumption is an important segment in the energy consumption in households in Serbia, where majority of households heat water with electric resistance storage water heaters. A more appropriate alternative is installation of solar water heating (SWH) systems in households. The current number of installed SWH systems in Serbia is negligibly small – only about 0.1% of all households. Serbia has recently adopted feed-in tariffs for generating electricity from renewable energy sources (RES), but it did not provide any incentive for SWH installations. It is generally accepted that best form of SWH incentive is a direct subsidy to reduce high upfront costs. The aim of this work is to suggest the level of the subsidy which Serbian government should offer in order to reach the level of SWH deployment comparable to that of more developed countries. After financial analysis of SWH installation in six Serbian cities, followed by contingent valuation survey among household owners in Serbia, it is concluded that 20% subsidy is justified already by CO2 mitigation potential of SWH systems, while 50% subsidy, which lowers equity payback period to 5.5–6 years, generates most interest among household owners.

Optimization of equipment capacity and an operational method based on cost analysis of a fuel cell microgrid

A microgrid requires a stable supply of electric power and heat, which is achieved by the cooperative operation of two or more pieces of equipment. The equipment capacity and the operational method of the equipment were optimized using a newly developed orthogonal array-GA (genetic algorithm) hybrid method for an independent microgrid accompanied by a fuel cell cascade system, solar water electrolysis, battery, and heat storage. This type of system had not been hardly developed until now. The objective function of the proposed system was the minimization of the total amount of equipment and fuel cost over ten years. For the first step in the proposed analysis method, the capacity of each piece of equipment and the operational method, which are considered to be close to the optimal solution of the system, are combined using the orthogonal array and factorial-effect chart, which are an experimental design technique. In the next step, the combination described above provides the initial values to the GA, and the GA searches for the optimal capacity and operational method for each piece of equipment in question. Compared with a simple GA, the convergence characteristic improves greatly using the proposed analysis method developed in this study.

The influences of air heat storage, plant photosynthesis and soil water movement on surface energy balance over the loess plateau

The surface energy imbalance problem has become a challenge in the study of surface land process since it was found in the late 1980s. By using data provided by the program the Loess Plateau Land-surface Process Experiment (LOPEX) and introducing the vertical sensible heat flux into the surface energy balance equation, in the paper, we estimate the heat storage associated with change of air temperature and humidity as well as the energy stored in plants due to the photosynthesis, determine the water vertical flux in the shadow soil layer both by water conservation principle and two-level soil temperature, and investigate the influences of air and plant photosynthesis energy storages and heat transferred by the soil water movement on the surface energy budget. It is found that the diurnal variation peaks of averaged energy storages of air and plant photosynthesis reach 1.5 and 2.0 Wm-2 respectively. Additionally, the diurnal variation peak of mean heat transferred by vertical water movement is close to 8.0 Wm-2. The closure of energy balance is improved from 88.1% to 89.6% by adding the three additional energy terms to the energy balance equation. As a whole, the energy storage related to air and the plant photosynthesis, and the heat transferred by the soil water movement both promote the surface energy balance to some extent. Furthermore, the semi-arid climate and the vegetation condition of Loess Plateau essentially lead to significant differences of energy storage be tween this area and other climatic districts.

Experimentation of a Plane Solar Integrated Collector Storage Water Heater

In order to popularize the use of the solar-water heaters, especially in the residential and tertiary sectors with the third world, it appears to be necessary to reduce their cost while improving their performances. It is the object of this integrated storage collector thus created and tested in the south of Tunisia. It is simply made up of a tank playing the double part of solar absorber and storage tank of warm water, of a glazing to profit from the greenhouse effect and of an insulating case. Its measured energy performances, by the method of input-output proves its effectiveness to produce hot water, in spite of its simplicity of manufacture, usage and maintenance. Indeed a temperature of water exceeding 70?C is reached towards the afternoon True Solar Time, and for an efficiency of 7%. Thus, this type of collector with integrated storage is entirely satisfactory and could be available to larger mass.

The Effects of Boundary Design on the Efficiency of Large-Scale Hot Water Heat Stores

Boundary design of stratified hot water heat stores is important not only to minimize the thermal losses to the ambient but also to preserve the thermodynamic quality of the stored energy. A new method of characterization, which equivalently accounts for both these concerns, is applied in this paper to investigate into the boundary design of large-scale hot water heat stores. A variety of concepts related to general design of the containments, namely, the effects of the thermal conductivity and thickness of the container wall, are numerically analyzed. The design insights provided by the analysis are in good agreement with the corresponding experimental results for small-scale hot water heat stores found in the literature. Different ways of insulation application, differential application of the external insulation, and insulation of the top walls are further investigated to obtain ideas for the efficient use of the insulation material. The new characterization scheme proves to be an efficient tool to rank the performance of different boundary designs during storing process of large-scale stratified hot water heat stores and to provide valuable design insights.

2중 단동비닐하우스의 태양열 축열이용 효과

This study was carried out in order to reduce the amount of underground water which is used in the double layered single span plastic greenhouse for retaining heat. For this research, two plastic green houses of the double layered single span plastic greenhouse were installed. There was equipped of internal small tunnel for keeping warm air in the interior of the house. Then the internal small tunnel for keeping warm air was fitted with PVC duct of 50 cm in diameter filled with subsurface water. The surplus solar energy in the greenhouse was stored in the water in the PVC duct. Four FCUs (Fan Coil Unit), which has the capacity of 8,000 kcal per hour, were installed in the middle of the house, and a circulation motor in heat storage water tank was operated from 10:30 a.m. to 16:00 p.m. in order to circulate water between the water tank and the FCUs. Consequently about 5 degrees celsius could be maintained in the interior of the internal small tunnel for keeping warm air with the external temperature of lower than minus 5 degrees celsius. It appeared that the alteration of an internal temperature of the house was flexible depending on the sunlight during daytime. To prevent the water freezing, mixing antifreezing liquid in the water or operating FCU continuously was needed. Also, in order to use the surplus solar thermal energy on plastic green house of water curtain system efficiently, storing the surplus heat during daytime simultaneously finding a method of using water curtain systematic underground water happened to be important. As a result of this research, when the house's interior temperature is below zero the operation of FCU appeared to be impossible. Considering the amount of water used in the house with water-curtain-heating system is 150～ 200 ton per day, using the system mentioned in this research showed that reducing the underground water more than 80% in order to maintain the internal temperature as the level of 5 degree celsius at the extreme temperature of minus 5 degrees celsius.

The Air-Conditioning Rtilization of Natural Cold Resource of Lakes and Reservoirs

In the reservoir water temperature conducted annual test, test data shows that water temperature perennial remain in 9 ~ 10 in certain depth below. Reservoirs and lakes are huge natural cold source. In an air conditioning engineering, the reservoir cold water was directly used as cooling source. The air conditioning effect is good and to gets good energy-saving and environmental benefits. It suggests that solar energy, natural ventilation and natural cold and heat storage in water should be widely used in the western tourist architecture in order to achieve low carbon tourism.

The Implication of Solar Hot Water System in Small High-Rise Buildings

It introduces small high-rise building concepts, discusses the calculation of solar hot water system, which includes the collection of raw data, the determination of solar collector area, the size of heat storage water tank and hot water system type as well as summarizes it as a reference for engineering design.