A Graduate Research of the Hybridization of High Concentrated Solar Panel and Anaerobic Production and Desalination

High concentration photovoltaics (HCPV) have become popular new types of solar technology. Compared to traditional photovoltaic panels, HCPV systems are potentially more efficient and cost-effective. However, HCPV’s operation will cause high temperature on the panel surface, which causes a heat waste and deficiency of HCPV. Meanwhile, the anaerobic production and desalination plant need a highly demand of heat resource. The paper uses TRNSYS software to design a hybridization system with 500 suns concentration’s HCPV, multi-stage flash desalination and anaerobic tank. The 0.01 m2 size HCPV system achieves a max electricity output at 300 W. Meanwhile the hybridization can operate desalination plant with 0.5 distillation ratio and anaerobic digestion at 3.2 m3 per hour. The study of a graduate research of the hybridization of high concentrated solar panel and anaerobic production and desalination would fit the call in the graduate division and it is consistent with the division objectives. Furthermore, the study is relevant to the ASEE division’s mission and the scope is interdisciplinary including design, development and research. The research paper is relevant to Chi Xu’s Ph.D. dissertation. Furthermore, the information is also used in a graduate level public works engineering and management class that is offered each fall semester. This makes it relevant to the theme of the ASEE Graduate Studies Division. Introduction The solar energy is an ideal energy can gain from the sun, as a type of renewable energy, solar energy has its advantage: widespread, low contamination and flexibility. High concentrated photovoltaics is new solar technology which can produce electricity cost-effectively. By using a reflection system to concentrate solar radiation can decrease cost and increase the efficiency. HCPV uses cooling system to cool down the high level heat received from solar concentration. However, cooling system can’t use the potential energy from the heat, thus the heat is ‘waste’. In order to reuse the energy and demonstrate the concept of renewable energy, the paper will design the hybridization the HCPV and biogas production and desalination plant to reuse waste heat from HCPV and maintain the HCPV in high efficiency. Compared to normal separated plant, the hybridization can provide electricity, biogas and fresh water economically. A model will be built to demonstrate the performance of hybridization. The paper will illustrate the efficient importance of hybridization, the hybridization can achieve a better combination to society and industry. The paper also demonstrate a direction of clean energy hybridization in future research. HCPV The high concentrated solar panel has its advantages: greater efficiency, high energy density and lower module surface area [1]. The present HCPV efficiency can reach 39% when using multi-junction cells [2]. However, the efficiency of the photovoltaic cell is affected by temperature, in HCPV system, solar concentration ratio dominantly controls the temperature [2], which is shown in Figure 1. Figure 1. Photovoltaic cell efficiency trend in different concentration ration. The trend of cell efficiency and temperature can be seen in Figure 2. When the PV cell temperature increasing, it decreases the conversion efficiency of the PV system [3] Figure 2. Photovoltaic cell efficiency trend in different temperature. HCPV plant uses a large quantity of water for cooling the system to keep HCPV running in a moderate efficiency. However, the cooling system maintains the HCPV in operational condition. And the water from the cooling system can still be used as a source of energy. At present, this water is wasted. The cooling system water can be utilized in a biogas plant as a source of energy to maintain the anaerobic tank at a 35 Celsius degree temperature. The objective is to create a co-location environment that includes the hybridization of HCPV, biogas and desalination plants. The hybridization can reuse waste heat from HCPV and still maintain the efficiency of HCPV at a desirable level. The hot water from desalination can still be used as a heat source in biogas production. A model will be built to demonstrate the performance of hybridization and co-location environment. The co-location environment saves energy by utilizing the hot water produced from HCPV and desalination plant for producing biogas. Furthermore, the co-location environment keeps the cost of land, material, maintenance and transportation. HCPV types HCPV’s concentrator geometries conclude three types: single cells, linear geometry, and densely packed module. In the single cell, solar radiation focus onto each cell, single cell concentrator uses passive cooling to maintain temperature and efficiency [1, 4]. Linear geometry and densely packed module are usually used in large scale plants or to achieve a higher electricity outlet. The cell temperature of an HCPV module impacts its electrical output [5, 6]. Thus, HCPV needs a cooling system to maintain the temperature of the solar module. The cooling system can keep the temperature between 50°C and 80°C [7, 8], many different kinds of cooling system have been shown in literature in the past[9-11]. Passive and active cooling systems are two types of general cooling method for HCPV cooling. The passive cooling system uses a metal heat sink to cool down the panel. Many types of research show the ability to use passive heat sink to keep panel efficiently (especially in 500suns) [12-19], the passive cooling fin structure can be shown in Figure 3 [19]. Figure 3. Schematic of a finned heat sink: (a) front view and (b) 3D rendering. The nomenclature used (Figure 3) in the present work is: spacing (s), pitch (p), height (H), thickness (t), length (L), base width (W), and base thickness (tb) [19]. However, compared to active cooling systems, passive cooling system have lower heat dissipation rates, and environment conditions such as air temperature and wind speed will affect the heat dissipation rates [20]. Active cooling system concludes micro-channels, spray cooling and jet impingement, Abdolzadeh showed spray cooling could reduce cell temperature from 58°C to 37°C [21], however, spray cooling require water usage and the heat from the cell is wasted. The active cooling system is more efficient and more technically feasible if the waste heat from cooling system can be reused in other application [22]. Royne claimed passive cooling system can be used to single cell geometries in 1000 suns. However, more study shows that passive cooling is not efficient enough to cool down the cell especially in high environment temperature [23-26]. Aldossary concluded that active cooling can maintain PV operation efficiency under operating temperature limit and avoid solar cell lifetime degradation [26]. Sun found that the cell temperature can be controlled in 20°C to 31°C when using dimethyl silicon oil [27]. In the active cooling method, Water active cooling can be considered as a cost effective method when the heat from coolant can be reused. Haitham indicated the cell temperature can maintain between 36.6°C and 31.1°C when using active cooling [28]. Zhu found that module temperature can be cooled to 45°C when using water immersion cooling [29]. And Du also showed the water cooling can reduce the cell temperature under 60°C [30]. Aldossary shows the outlet temperature of water cooling can be reached 90°C when it is accessed to a large scales HCPV plant. The heat can be used for heat pump or other thermal application [26]. The active cooling varies from many different types, the paper will discuss them in the following section. Water cooling Lasich designed an active cooling system for densely array CPV with 200 suns, which is operating by water [31]. The system can keep a cell’s temperature at 40°C with 500 kW/m2 dissipating heat flux capability from cells. Kolhe found that the increasing of water flow rate will increase the electrical efficiency and thermal efficiency rapidly [32], the water cooling increases the CPV electrical output 4.7 to 5.2 times higher than original PV without concentration and cooling. Chong built an automotive radiator cooling system with CPV operating in 377 suns. They observed the efficiency increased from 22.38% to 26.85% in six hours. And the temperature of CPV cell decreased from 59.4°C to 37.1°C [33]. Jet impingement cooling Jet impingement cooling is an active cooling method which is usually used in industry. It injects a small amount of water into air jets and strikes the grinding wheel at certain speed [34]. Roney designed a jet impingement cooling for densely packed PV cells. In their system, water flows through plenum chamber to the heated surface, which decrease the temperature of PV cells from 60°C to 30°C (200 suns) and 110°C to 40°C (500suns) [35]. Liquid immersion cooling Russel patented a liquid immersion cooling system. In the system, the photovoltaic cells are placed in a long pipe which is immersed in liquid coolant [36]. Abrahamyan showed dielectric liquid can be used as coolant, in their research, they uses glycerin, butanol, acetone, dioxane, toluol, isopropyl alcohol and deionized water as experimental coolant, their experiment results showed dielectric liquid with 1 to 4 mm thickness can increase cell’s efficiency from 40% to 60%. Zhu also designed a liquid immersion cooling system for densely packed PV cells. They found the module was cooled to 3545°C under 2.0-2.7 m/s water flow rate and 16°C inlet temperature of silicon oil [37]. Desalination The desalination is a method to remove mineral salts from saline water and purify the saline water for domestic consumption, industrial usage, and irrigation. Desalination is an important fresh water income particularly in dry countries such as Saudi Arabia, and Australia. Desalination has following conventional methods: Multi-stage flash distillation Multi-stage flash distillation (MSF) is a desalination