Rural Electrification is one of the main applications of photovoltaic (PV) power systems. Stand-alone PV generators are suitable for use in rural households or villages that are located far from the national utility grid because extension of the grid system into rural villages is expensive, especially in developing countries. PV systems are already cost-effective for rural electrification of scattered houses and villages. There are many rural villages in Thailand located without access to electric power. Rural people have used kerosene lamps and candles for lighting applications. There are no facilities for community entertainment.
This research project focuses on the design and analytical evaluation of stand-alone PV power systems for rural areas in Thailand. Both centralised and decentralised PV systems were examined. A sample village with 100 households in a rural area at Udon Thani Province of Thailand was selected for design of a centralised PV mini-grid system according to daily load requirement in the village. The daily electrical energy needs of a village can be broadly split into three categories, namely (i) for each household, (ii) for a community centre and (iii) for public use. The design of a centralised mini-grid system is detailed. The system sizing and prediction of system performance, especially the best matching between the array size and battery storage capacity, were carried out using a computer programme in C-language developed in this research. Other programmes were also specifically developed to analyse the following topics: (i) estimation of solar radiation on inclined surfaces for Thailand. (ii) design of electrical power distribution (mini-grid) system, (iii) lightning protection
system and (iv) protective equipment sizing and conductor size.
One of the important parts of this research programme is the design of PV systems in decentralised applications. These are a battery charging station system, water pumping
system, public lighting system, community facilities' system and solar home system. These topics consider how system size is determined, how specific system hardware is
selected, what installations are good practice, and how the system's life cycle cost can be estimated. The worksheets are provided in an appendix for users as well as PV engineers. Analytical comparisons of each PV system type in terms of system cost. Possible benefits and problems for using in typical rural villages of Thailand have been addressed. Three PV applications for a Thai rural village, namely a mini-grid system, a battery charging system and a solar home system has been compared to determine the most advantageous. A strategic model for PV dissemination in Thailand has also been proposed emphasising the cost advantages of decentralised systems.
The results of this project are able to provide useful information for rural electrification planner and PV engineers to choose the optimum system for installation. They should be applicable in other countries with a similar climate and latitude angle.

Design and analytical evaluation of stand-alone photovoltaic power systems for rural areas in Thailand

The objectives of the power system design and choice of equipment are to ensure maximum security of supplies with operational flexibility at an acceptable cost. The paper describes the development of the design, from the conceptual pretender stage to the completion of manufacture of equipment ready for shipment to the site. In the development of the design a number of problems are identified, relating to the constraints of fault levels and voltage regulation on power systems with large induction-motor loads. Alternative solutions are examined, and reasons given for the solution adopted. The importance of computer modelling is emphasised in the analysis of power system design, not only for the solution of technical problems, but for optimisation to realise any cost advantages available. Finally, the authors indicate their views on future trends in system design for large power stations, and conclude that the objectives of supply security, operational flexibility and acceptable cost have been achieved at Castle Peak B.

G. Tuft

Papers

Design of the electrical power system