A comprehensive thermodynamic analysis of load‐flexible CHP plants using district heating network

Abstract

Summary Because of the rapid expansion of intermittent renewable energy, conventional coal‐fired power plants, including combined heat and power (CHP) plants, are required to improve the quick‐response ability to respond the changing demand of the grid. However, the flexibility of CHP plants is not easy to be improved because of the restriction of traditional load variation mechanism. This work presents a comprehensive thermodynamic analysis on the flexibility‐improving scheme using the thermal energy storage (TES) capacity of district heating (DH) network. A typical CHP plant and related DH network were selected as a case study. The flexibility demand under the context of renewables accommodation in the short timescale (counted by minutes) and the operational characteristics of CHP plants were analyzed on the basis of experimental data and thermodynamics. Besides, the influence of heat supply adjustment on heat users' indoor temperature was quantified with a dynamic model, and the thermal inertia of the DH network is discussed. Moreover, a thermodynamic model for the load variation processes simplified with operational characteristics was established to analyze the response ability improvement of CHP plants. Results of the case study show, the scheme can shorten approximately 34% of the response time while almost have no influence on the indoor temperature of heat users.

Minimum loads of coal‐fired power plants and the potential suitability for energy storage using the example of Germany

“…The need for improved flexibility 1,2 is mainly caused by weather-dependent generation technologies whose grid integration brings new challenges, 3 resulting in steeper and more variable residual loads 4,5 This leads to an increasing amount of low and negative prices at the wholesale markets, which results from nonresponding conventional power plants, especially coal-fired power plants, during low residual loads causing an irreducible minimum of conventional feed-in. 6 The reasons for the nonresponding behavior are technical, 7 economical, or stability limitations. As a result, the flexibility requirements 1,8 increase regarding the demand and the supply side, requiring more complex considerations of the challenging fluctuations from the demand, the residual load and the renewable energy infeed 9 by different market participants.…”

Optimal planning of multi‐energy microgrid with different energy storages and demand responsive loads utilizing a technical‐economic‐environmental programming

“…Although these resources planning may be taken into account more generally where various carriers are interconnected, which, for example, can mention the CHP units in micro‐smart grids. Each device of CHP connects electrical power and heating energy systems and also connects natural gas and electrical power networks 5 . Today, the balance between production and energy demand is of particular importance.…”

“…Each device of CHP connects electrical power and heating energy systems and also connects natural gas and electrical power networks. 5 Today, the balance between production and energy demand is of particular importance. To achieve this balance, the energy supply system employs a variety of solutions.…”

Quantitative Analysis of Energy Storage in Different Parts of Combined Heat and Power Plants

“…L. Fu [21] pointed out that ES in DHN can be used for increasing the flexibility of power generation by CHP plants. The control method using ES in DHN is given in [22][23]; nevertheless the ES capacity is only roughly estimated. ES in DHN can also be used for increasing the heat flexibility [24][25] or emergency repair of DHN [23].…”

“…The control method using ES in DHN is given in [22][23]; nevertheless the ES capacity is only roughly estimated. ES in DHN can also be used for increasing the heat flexibility [24][25] or emergency repair of DHN [23]. Although there is a lot of research focusing on the power and heat energy programming utilizing ES in DNH [26][27], the ES capacity is implied in the calculation.…”