1. Field of the Invention
The present invention relates to a system designed to manage energy (e.g., electric power or heat) at loads. More particularly, the invention relates to a technique of adjusting energy loads.
2. Description of the Related Art
In recent years, energy management systems have been proposed for use in buildings, factories, infrastructure and houses in order to increase the use efficiency of energy, such as electric power or heat. The energy management system includes a supply-and-demand control technique of using reproducible energy such as wind- or solar-generated power, together with the basic electric power, and matching the power generated with the power consumed. Further, energy supply systems, each including non-utility generation units, fuel cells and power storage devices (i.e., storage batteries), and methods of operating these systems have been proposed, too.
These systems are attracting attention as power supply system known as microgrid. A microgrid supplies not only the basic electric power, but also the power provided from equipment pieces such as solar generation units, wind generation units, batteries and fuel cells, and are used in accordance with the predicted demands and predicted supplies.
The microgrid is a system that predicts a demand for energy such as electric power or heat and also a demand for power that may be generated in uncontrollable generation equipment such as wind generation units and solar generation units. (That is, the microgrid performs both demand prediction and supply prediction.) In this system, the non-utility generation units, fuel cells and power storage devices (e.g., batteries) are so used or controlled in real time in order to matching the power generated with the power consumed. As a prior-art example of this system, an energy management system has been proposed, which has the ordinary demand prediction function of predicting the energy to consume and the supply optimization function of formulating an energy accumulation schedule. (See, for example, Jpn. Pat. Appln. KOKAI Publication No. 2002-245126.)
However, the microgrid does not control energy loads. It controls only equipment pieces, such as the non-utility generation units, fuel cells and power storage devices (e.g., batteries). Its adjusting ability and its installation cost should therefore be traded off. In the supply-and-demand control the microgrid performs, the predicted power demanded at each load is based primarily on the use of the load, not taking the desirable load adjustment into account. Consequently, the adjustment is greatly limited in the supply-and-demand control and in the system use planning. This will ultimately jeopardize the actual system operation. To solve this problem, the system tends to include an excessive number of equipment pieces, such as non-utility generation units, fuel cells and power storage devices (i.e., storage batteries).
On the other hand, systems having a demand-side management (DSM) or a demand-side control (DSC) function (i.e., load control or load adjustment), which controls energy load equipment pieces, are now attracting attention. More precisely, the system has the function of setting power rates to promote the adjustment of loads. (See, for example, JPN. Pat. Appln. KOKAI Publication No. 2002-271981.) In this system, the consumers voluntarily adjust the loads in accordance with the power rate, accomplishing indirect load adjustment. As a system having the function of adjusting loads, an indirect load adjusting system is proposed, which adjusts the power rate, thus incentivize people to adjust the loads. (See, for example, Jpn. Pat. Appln. KOKAI Publication No. 2002-176729.)
To achieve demand-side management (DSM) in any energy management system having the DSM function, the overall power load must be limited for a forced load shutdown (selective load shutdown) and the load leveling must be performed by using the load outside any peak use period, that is, by shifting the load use period. In order to take these measures appropriately, a priority order in which to shutdown the loads and a specific rule of adjusting loads should be predetermined. This is a forced method, in which the conditions at any load are neglected. In other words, no energy management system is implemented to adjust the loads effectively in accordance with the energy required at the loads or with the conditions of the loads.