Solar absorption cooling in Spain: Perspectives and outcomes from the simulation of recent installations

In spite of the fact that Spain is one of the EU countries with the highest solar resource on annual basis, the huge seasonal variation in solar radiation availability and the relatively short period with heating demand, make it difficult to reach significant contributions of solar energy to the buildings heating energy demand. This compromises the economic viability of big solar collector areas per capita, and introduces technical difficulties for the dissipation of the excess solar energy available in the summer months. On the other hand, in a large part of the Spanish territory, in other to reach adequate comfort conditions in our buildings, the energy demand for cooling is more important or of the same order than the heating demand. Cooling energy demand is now experiencing a fast growing rate as this comfort requirement becomes internalized. Domestic air conditioning equipments based on vapour compression cycles are being used to reach comfort conditions in some of the rooms of buildings that were designed without taking into account cooling requirements. In spite of their so far small contribution to the total building sector energy demand, these equipments are already imposing important constraints on the environment and the electricity distribution system. Solar absorption cooling arises as an interesting alternative, which at the same time allows reaching a higher solar contribution to the heating demand. However, solar cooling installations present several peculiarities with respect to the more known DHW or even heating installations, which require to incorporate a more detailed approach and additional considerations in the design and performance evaluation processes. Besides, some limitations still persist in solar absorption systems, which could make them loose their market potential for the benefit of other solar cooling options. In this paper, we present some conclusions arising from the experience gained in detailed TRNSYS dynamical simulation of some of the first commercial solar heating and cooling installations recently implemented in Spain, and analyse their perspectives in comparison with other solar cooling options.     

项目规模对地埋管土壤热平衡的影响研究

项目规摸（地埋管规摸）对土壤源热泵系统土壤全年热平衡问题影响至关重要,因此本文针对不同规模、不同冷热负荷比情况下地埋管土壤温度变化进行了研究分析,结果表明,当建筑全年累计冷热负荷比从1：1变化至4：1时,地埋管区域土壤10年累计温升从4．18℃升高到9．11℃,影响较大;对于5～10口井的小规模建筑,即使当建筑累计冷热负荷比达到4：1时,热平衡问题都可以忽略不计,但是当地埋管规摸增至20口管井时,热平衡问题必须要予以重视。最后,本文针对小规模建筑应用土壤源热泵系统时如何缓解并解决土壤热平衡问题进行了研究,为土壤源热泵系统的研究和应用提供了理论支持。     

Optimization of a thermal storage unit combined with a biomass boiler for heating buildings

The performance of a boiler with a built-in thermal storage unit is presented. The thermal storage unit is an insulated water tank that absorbs surplus heat from the boiler. The stored heat in the thermal storage unit makes it possible to heat even when the boiler is not operating, thus increasing the heating efficiency. A system with three components is described. The model of the system and the mathematical model were made using the TRNSYS program package and a test reference year (TRY). The degree of efficiency, which optimizes the thermal storage volume and the heating power of the boiler, was determined. The thermal storage must also ensure that the heat is stored at the highest possible exergy level, and complete mixing of the water is a condition for optimizing the thermal storage. The matching of the boiler’s heating capacity with the thermal storage unit ensures a supply of heat even when the boiler is not operating.     

基于TRNSYS的空调水系统管网模型的建立

建立了空调水系统的管网模型并应用于TRNSYS中,以某假日酒店为研究对象,建立了其空调系统的动态仿真器。对酒店空调系统在末端无控时的水力特性以及末端有控时的能耗情况进行了仿真计算,结果表明,管网模型的引入可利用TRNSYS仿真研究空调系统热力特性和水力特性。     

Experimental investigation and theoretical analysis of solar heating and humidification system with desiccant rotor

In this paper, a solar heating system, which combines the technologies of evacuated tube solar air collector and rotary desiccant humidification together, has been configured, tested and modeled. The system mainly includes 15 m² solar air collectors and a desiccant air-conditioning unit. Two operation modes are designed, namely, direct solar heating mode and solar heating with desiccant humidification mode. Performance model of the system has been created in TRNSYS. The objective of this paper is to check the applicability of solar heating and evaluate the feasibility and potential of desiccant humidification for improving indoor thermal comfort. Experimental results show that the solar heating system can convert about 50% of the received solar radiation for space heating on a sunny day in winter and increases indoor temperature by about 10 °C. Compared with direct solar heating mode, solar heating with desiccant humidification can increase the fraction of the time within comfort region from about 10% to 20% for standalone solar heating and from about 30% to 60% for solar heating with auxiliary heater according to seasonal analysis. It is confirmed that solar heating with desiccant humidification is promising and worthwhile being applied to improving indoor thermal comfort in heating season.     

Eco Insulation Materials： Reduction of Cooling Loads of a House Made of Breeze Block or Laterite in a Dry Tropical Climate

In this paper, we study the influence ofeco materials for roof insulation and fiber-reinforced mortar coatings on cooling loads of a home in dry tropical climate. The walls of the house are made of cinderblock or laterite and the insulating material of a roof panel is made with lime （24%）, cement （6%）, water （50%） of vegetable fibers hibiscus sabdariffa （16%）, tree widespread in Burkina Faso and sugar cane bagasse （4%）. This panel roof insulation and the fiber-reinforced mortar were characterized at the Laboratory of Physics and Chemistry of the environment by the hot plate method. The building is modeled in TRNSYS using climate data from the city of Ouagadougou. The results obtained show that in the warmer months of the year, that is to say in March and April, the relative differences between heat gains the configurations ＂breeze block-coating mortar and roof not insulated＂ and ＂laterite- fiber-reinforced mortar coating and insulated roof＇ vary between 15.6% and 16.8%. The configuration ＂laterite-fiber-reinforced mortar coating and insulated roof allows a reduction of annual heat gains of 15.5% compared to the configuration ＂breeze block-coating mortar and roof not insulated＂.     

TRNSYS simulation for solar-assisted liquid desiccant evaporative cooling

ABSTRACT

Recently, desiccant cooling systems are well thought of as a competent method for controlling the water content in the air. A solar flat-plate collector has been used as it decreases the dependency on non-renewable resources. Solar-aided liquid desiccant systems have been used to reduce the dependency of air-conditioning systems on non-renewable sources of energy. Manipal’s humid and searing climate provides certain benefits in setting up such a system. The suggested system has reliability and equipment life and also takes complete advantage of the available solar energy for the renewal of the liquid desiccant. TRNSYS simulation is used to predict the efficiency and feasibility of the system. The temperature and energy-load variations were successfully obtained. An effective simulation was developed whereby the solar air conditioning of a room was indicated.     

基于TRNSYS的区域供冷能源站仿真控制研究

以泰州医药城区域供冷系统为研究对象,在TRNSYS中建立了区域供冷能源站模型。对能源站中的五台热泵机组采用组合式控制,模拟了冬夏季节的热泵机组联合运行时的供回水温度。     

太阳能低温地板辐射采暖的TRNSYS模拟研究

利用TRNSYS对兰州地区的气象资料进行模拟分析,通过对建筑外围护结构的节能设计和低温地板辐射采暖的热舒适性研究以及兰州地区太阳辐射的特点探讨了太阳能与低温地板辐射采暖的互补优势,充分发挥建筑节能的特点。     

Experimental validation and sensitivity analysis of a coupled BES–HAM model

In this paper the ability of a coupled BES–HAM model to reproduce realistic data is evaluated by comparing numerical results with measured data from a climatic chamber experiment. Calcium silicate plates are introduced into a test room and a small calcium silicate sample is installed in one of the walls. The response of the test room to relative humidity variations of the supply air is evaluated, while the supply air temperature is kept constant. The measurements confirm that due to the presence of hygroscopic materials in the test room, the relative humidity variations in the room are damped. The calculated temperature and relative humidity in the middle of the test room are well within the uncertainty interval of the measurements. On the other hand the coupled model predicts a larger damping and phase shift of the relative humidity variations inside the sample, yet the agreement between the calculated and the measured temperatures in the sample proves to be good. Finally, a sensitivity analysis is performed to evaluate the dependence of the numerical results on the uncertainty of the input parameters. It is demonstrated that by using a lower vapour resistance factor for the calcium silicate material, the agreement between the measured and calculated data is improved.