Combined heat-and-power plants and district heating in a deregulated electricity market

In the last decades one of the most difficult problems in the electricity market has been how to dispatch and manage the electricity in power generation plants. Despite of all the benefits of distributed poly-generation and combined heat and power systems, their penetration in the power market worldwide is quite modest and one of the barriers against their increasing participation is the high fees for back-up supplies, which is one of the problems addressed in this investigation. This paper introduces a pool of distributed generation units (named nerve-centre) able to economically optimise the generation schedule of gas turbine power plants and end-users interconnected through a mini-grid. A hybrid genetic algorithm adapted priority list was developed to solve the multi unit generation schedule optimisation problem. The algorithm developed in this study leads the optimisation mechanism to a faster convergence and a very low risk of non-convergence to the optimal result. Despite the power generation optimisation studies reported in the technical literature, none of them has been modelled for such a pool of distributed generators trading electricity in the competitive market. This investigation shows that the proposed nerve-centre concept can result in significant savings to generators/end-users.

Download Full-text

Increasing the Flexibility of Combined Heat and Power Plants With Heat Pumps and Thermal Energy Storage

Journal of Energy Resources Technology ◽

10.1115/1.4038461 ◽

2017 ◽

Vol 140 (2) ◽

Cited By ~ 23

Author(s):

Eike Mollenhauer ◽

Andreas Christidis ◽

George Tsatsaronis

Keyword(s):

Thermal Energy ◽

Electricity Market ◽

Power Plants ◽

Combined Heat And Power ◽

Heat Pumps ◽

Optimal Operation ◽

Mixed Integer ◽

Steam Turbines ◽

Mixed Integer Linear Program ◽

District Heating System

Combined heat and power (CHP) plants are efficient regarding fuel, costs, and emissions compared to the separate generation of heat and electricity. Sinking revenues from sales of electricity due to sinking market prices endanger the economically viable operation of the plants. The integration of heat pumps (HP) and thermal energy storages (TESs) represents an option to increase the flexibility of CHP plants so that electricity can be produced only when the market conditions are favorable. The investigated district heating system is located in Germany, where the electricity market is influenced by a high share of renewable energies. The price-based unit-commitment and dispatch problem is modeled as a mixed integer linear program (MILP) with a temporal resolution of 1 h and a planning horizon of 1 yr. This paper presents the optimal operation of a TES unit and a HP in combination with CHP plants as well as synergies or competitions between them. Coal and gas-fired CHP plants with back pressure or extraction condensing steam turbines (STs) are considered, and their results are compared to each other.

Download Full-text