Janis Shipkovs

Dynamic Simulation for Increasing the Efficiency of Solar Cooling Systems in Northern Latitudes

Latvia lies on the eastern shores of the Baltic Sea at 57°00′N latitude. In Latvia, cooling is required about 1500 k.h degree hour (at an indoor temperature of 21 °C). This chapter presents the optimization of a solar cooling system in Latvia using the model of a solar cooling system which was created by a dynamic simulation program. The model is similar to the existing real solar cooling system installed at the Institute of Physical Energetics. The precision of the model was tested by comparing it with real equipment. Simulations were carried out using metrological data from different European countries. Simulation results, the dependency of the heat carrier average temperature and the ratio of energy from a pump to the system were collected and analysed. Different element locations of the solar cooling system were compared in two models. The annual cool production of the solar cooling system was defined.

Investigation of solar collector´s in Latvian conditions

Outdoor air temperature range in the Baltic region i s below average values in Europe. Range of outdoor air temperature in the Baltic region is -3 oC in winter and +16 oC in summer. And solar radiation intensity is lower in comparison with the average European values. The average solar radiation intensity reaches 1100 kWh/m2 per year in Baltic region. Therefore, there is a particular need to optimize the solar thermal system in the Baltic region. Solar collectors operation methods investigated on the IPE solar energy polygon according different parameters. The most common types of solar collectors operation were investigated and compared: by the time, by the heat carrier temperature differences of input and output, by the solar radiation intensity and operation control methods in various combinations. Theoretical and practical advantages and disadvantages of using each control methods were analyzed. Solar collectors operation system could be regulated in accordance with the solar radiation intensity, by the boiler lower temperatures and by the outdoor air temperature to determine precisely the solar collector efficiency of the parameter changes. This may help to avoid the previous operation systems testing regime deficiencies. The precision of solar collectors operation depends on the type of operation systems: heat losses and the collector efficiency calculation accuracy, the sensor is accuracy, the time between the regulation regimes, and the range of heat carrier pumps action operation sensors. Currently, companies that offer solar collectors, offer solar collectors complete set with all necessary equipments for the solar collector connection for hot water supply system, or for home heating operation system by the temperature difference of input and output. And no one of them does not offer solar collectors operation systems by the various parameters.

The Mathematical Description for the Heat Conduction Process on Planesurfaces of a Solar Collector’S Absorber

The paper gives a mathematical description for the heat conduction proceeding on the plane surface of a solar collector’s absorber divided into three parts for each of which the Laplace equation with boundary conditions is formed. Applying definite approximations the authors have completely described mathematically the heat conduction process initiating in the plane part of a collector’s absorber, then passing to a tube and from the tube to the liquid flowing through it. In all the three absorber’s parts the process is considered stationary, independent of time, and, therefore the temperature field is obtained in spatial coordinates.