Under certain technical and economic conditions, a part of hydropower resources can be developed and utilized. According to the degree of resource development possibility, hydropower resources are classified into three levels, namely: theoretical reserves, technically exploitable resources and economically exploitable resources. According to the current technology and economic level, the exploitable resources are mainly river hydropower resources, tidal energy resources account for a small part, and the utilization of wave energy is still in the experimental stage. Hydropower resources are renewable energy sources, and statistics are generally based on the average annual power generation over many years.
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1.Theoretical reserves
Theoretically exploitable hydropower resources (reserves). For the river water energy resources, after calculating the energy by the average flow (or flow in the middle water year and low water year) and the subsection water level drop of the river, the accumulated number is the theoretical water energy resource of the river. According to the theoretical formula Calculated potential energy contained in the river water body. In the formulas for calculating the theoretical reserves, it is assumed that the amount of water passing through the river and the water level difference of the calculated reaches are fully utilized, and the energy conversion efficiency is assumed to be 1. The calculation accuracy varies from country to country. Some are calculated according to ground runoff and height difference; some are calculated according to precipitation and ground height difference.
The theoretical reserves of hydropower resources of a river, a water system or a region is the sum of the theoretical reserves of all river sections within its scope.
2.Technology can develop hydropower resources
Technically exploitable hydropower resources, that is, hydropower resources that can be developed and utilized according to the current technological level. According to the hydrology, topography, geology, reservoir inundation loss and other conditions of each river, the hydropower stations that may be developed are drawn up after preliminary planning, and the installed capacity and average annual power generation of these hydropower stations are counted, which are called technically exploitable resources. In fact, due to the limitations of engineering and technical conditions or other natural and social conditions, theoretical hydropower resources cannot be fully utilized in rivers and bays, and there will be certain losses when converted into mechanical energy and electrical energy. Therefore, technically exploitable hydropower resources smaller than the theoretical hydropower resource.
The multi-year average annual power generation based on technically exploitable resources is much less than the theoretical reserves. The difference is that when calculating technically exploitable resources, there are three points that are different from calculating theoretical reserves, namely: (1) resources that are not suitable for development of river reaches are not included; Factors such as fluctuations and losses in the water delivery process of the water diversion system, resulting in part of the water volume and water head not being used; ③ using the actual possible energy conversion efficiency, η<1.0. Since the technologically exploitable resources change with the development of technological level and social and environmental conditions, the quantity of technologically exploitable resources also changes with the development of time.
3.Economically available hydropower resources
Economically available hydropower resources. On the basis of technically exploitable hydropower resources, according to the conditions of construction cost, inundation loss, transmission distance, etc., technically feasible and economically reasonable hydropower stations are selected for statistics, and the economically available hydropower resources are obtained. According to the requirements of regional economic development, after analysis and comparison with other energy sources, the hydropower stations that can be developed that are considered to be economically favorable will be counted according to their installed capacity and average annual power generation for many years. The economically exploitable hydropower station is selected from the technically exploitable hydropower station group, so its value is smaller than that of the technologically exploitable resource. Economically exploitable resources are related to social and economic conditions and the relative economy of various power sources, so their quantities are constantly adjusted.
Due to the continuous improvement of the technical level, the continuous changes of economic conditions and the improvement of environmental protection requirements, the technically exploitable hydropower resources and the economically possible hydropower resources also change accordingly. Both technical and economic factors are generally considered to some extent when estimating hydro resource figures. Countries around the world generally use "potentially developed hydropower resources" to comprehensively consider the hydropower resources that may be developed technically and economically.
On the basis of the above three estimation methods, according to the requirements of ecology and environmental protection, some experts and scholars have begun to put forward the concept of "water energy resources available under the premise of ecology and environmental protection", that is, in the context of ecological and environmental protection Under the premise, a development plan for hydropower resources is proposed, the amount of available resources is determined, and the ecology and the protection of the environment are paid attention to in the process of hydropower resource development and utilization.