(94d) An MILP Model for Integrated Carbon-Free Heat Networks Considering Alternative Energy Vectors

An MILP model for integrated carbon-free
heat networks considering alternative energy vectors

André Prates Pereira, Sheila Samsatli*

Department of Chemical Engineering,
University of Bath, Claverton Down, Bath BA2 7AY, UK;

s.m.c.samsatli@bath.ac.uk

Space and water
heating contribute significantly to society’s demands for energy: heat demands
can be several times higher than those for electricity.  These demands are
primarily satisfied through natural gas.  The cleaner alternative of utilising
renewable (or nuclear) electricity along with heat pumps is limited by the
capacity of the existing electricity networks and the mismatch of available
renewable energy supply to the demands (e.g. solar power is more abundant in
the summer when heating demands are the lowest).  An alternative approach that
overcomes these limitations is therefore needed and the utilisation of hydrogen
as a carrier of energy may be a suitable candidate.  Low carbon hydrogen can be
generated from renewable electricity using electrolysers or from natural gas
through SMR coupled with CCS.  Both produce clean hydrogen that has a
significant advantage when used as a carrier for heat:

1.   
It can be
transported with little loss of energy, which is an advantage over electricity
networks, which have losses of about 8% of production, and certainly much lower
losses than transporting heat through a hot-water network.  District heating
networks are limited in scale due to the cost and inefficiencies of
transporting heat long distances. Therefore, hydrogen opens new possibility for
centralised generation of heat and long distance transport to the points of
demand.

2.   
Hydrogen can be
stored with little or no loss.  If electricity and heat pumps were to be a
solution to the problem of supplying clean heat at the national level, then
electricity storage devices will need to be developed that can efficiently
store large quantities of energy for long periods of time (inter-seasonal) and such
devices may not be available for the foreseeable future.  Long term direct
thermal storage is generally not possible due to the difficulty in insulating
the storage devices.  Thus hydrogen offers a natural solution. Natural gas is
also very well suited to storage but using natural gas in domestic boilers
results in CO₂ emissions.

We will present
the MILP model that we are developing that can be used to explore different
scenarios for generation, storage and transportation of hydrogen to satisfy
heat demands. The model considers the spatial distribution of heat demands and
the availability of primary resources in order to make a comparison between
centralised and distributed generation, as well as to determine the location of
hydrogen plants and storage facilities. The temporal representation
simultaneously captures the short-term operational issues and long-term
planning decisions (up to 2050) to examine different pathways from now to
various potential solutions. The model optimises the design and operational
decisions to determine the most cost effective/environmentally-friendly
transition to the future heat network while also determining what that network
should be.  There are many possible configurations and we will identify and
present the most promising ones.