A cogeneration plant supplying a single building
or connected to a small DH network is usually heavily
dependent on the heat demand. Long-term heat storing
can make it possible to produce more electricity
in the cogenerationplant, to use biofuels or other
renewable fuels instead of fossil fuels and to
connect new areas to the network. The investigation
of these issues requires knowledge on the heat
load profiles of the network and the electricity production
of the cogeneration plant. In addition to thermal
storage, the cogeneration can be improved by using CHP
process configurations which have high power production
efficencies at partial heat loads.
Objectives/goals
The objective of this project is to evaluate and
develop approaches that will inprove the economic
feasiblity and the thermal efficiency of cogeneration
through better utilization of the produced heat and
higher power generation in the CHP plant. The results
can be applied both in cogeneration plants producing
electricity, heat and cooling for a single building
and in a district heating network system situated
in or near areas with low heat densities. The economic
feasibility of cogeneration in small DH networks is
currently low and should be increased for future expansion
of district heating.
In this project, a general load model will be constructed
for esimating demand profiles for simultaneous DH and
power loads. The model will be needed for both considering
the suitability of CHP and long-term thermal storages
(storage period longer than a few days) for the total
system and for finding the best conditions for thermal
storage use in the system. Long-term thermal storages
and their usability for supplying heat or cooling in
low heat density areas e.g. to new housing or industrial
areas situated at longer distances from the existing
main network will be investigated. Also possibilities
for the combined use of cogeneration plants and long-term
storages either connected to a single building or a
small DH network will be considered. The power production
of the cogeneration plants will be improved by searching
the most efficient way to utilise the thermal storages
with one or several CHP plants and by selecting those
modules to the CHP process which have the economically
feasible electrical efficiencies also during part load
operation.
The goal of the project is to provide new possibilities
to increase economical feasibility and thermal efficiency
of cogeneration plants with efficient utilization of
the produced heat with long-term thermal storage. This
enables more efficient electricity production even in
lower heat loads and gives possibilities to expand the
district heating production to low heat density areas.
Also the possibilities to increase the power porduction
in the cogeneration pocesses are investigated. A model
for heat and power loads is developed as well as an
optimisation method for the most efficient thermal storage
integration to the cogeneration plant and to the network.
Work progress
Start of the project: June 2005.
Target audience and Benefits
The results are useful for district heating companies
looking for possibilities to expand their networks
to new and possibly remote residential or industrial
areas. Also the manufacturers of smaller cogeneration units benefit from
the improved heat utilization possibilities. Manufacturers
of steam cycle CHP plants can utilize the results
for improved electrical efficiency of the process
and for optimal integration of plants with a thermal
storage.
The results are assumed to benefit all participating
countries, e.g. Sweden, which have a low share of
CHP and rural areajs with small DH networks. Countries
like Finland with small heating plants, that would
need a profitable way to include electricity production
in these processes would benefit from the project,
as well as countries like Denmark that are actively
developing small-scale CHP and DH systems to serve
small communities. The more credible heat and electricity
demand profiles benefit many countries, e.g. Norway,
when the profitability of cogeneration use in a new
site is evaluated. Countries, like UK or Canada, which
have relatively low shares of DH connected with CHP
can use the results when they are looking for new
ways to increase the efficiency and the market share
of cogeneration. Countries like Netherlands, which
are aiming to maximize the environmental benefits
of their small-scale CHP plants connected to DH networks,
will benefit from the results.
