Page 1 - Water-energy_2020

Energy Conversion and Management 220 (2020) 113043

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Energy Conversion and Management

journal homepage: www.elsevier.com/locate/enconman

Water-energy nexus: A thermoeconomic analysis of polygeneration systems
T
for small Mediterranean islands
a, ⁎
a
a
Francesco Calise , Francesco Liberato Cappiello , Maria Vicidomini ,
Fontina Petrakopoulou-Robinson b
a
Department of Industrial Engineering, University of Naples Federico II, Naples, Italy
b Department of Thermal and Fluid Engineering, Universidad Carlos III de Madrid, Spain

ARTIC L E I NF O ABSTRAC T

Keywords: This paper focuses on the energy-water nexus, aiming at developing novel systems producing simultaneously
PV energy and water. This work investigates two solar polygeneration plants for the production of thermal and
CPVT cooling energy, electricity, and desalinated water for two small Mediterranean islands. In this case, seawater and
Solar desalination
solar energy are largely available, whereas freshwater is scarce and extremely expensive. The work also aims to
RO compare different technologies included in the polygeneration systems. In particular, the first plant is based on
MED
concentrating photovoltaic/thermal solar collectors, producing electric and thermal energy. The thermal energy
Polygeneration
is used to produce space heating, domestic hot water and space cooling by means a single-stage Lithium
Bromide/Water absorption chiller. An electric auxiliary chiller is also included. A multi-effect distillation unit is
included for freshwater production supplied by the concentrating photovoltaic/thermal collectors solar energy
and an auxiliary biomass-fired heater. In the second plant, a photovoltaic field is coupled with electric driven
technologies, such as heat pumps for space heating, cooling and domestic hot water production and a reverse
osmosis unit. The solar electrical energy excess is delivered to the grid. The third polygeneration plant includes
the same components as the first layout but it is equipped with a reverse osmosis unit. Two main case studies,
Favignana and Salina islands (South Italy) are selected. The heating, cooling and electric hourly loads of some
buildings located in both investigated weather zones are calculated in detail. In particular, space heating and
cooling loads are calculated by means of the Type 56 of TRNSYS (version 17), coupled to the Google SketchUp
TRNSYS3d plug-in. The buildings geometry, envelope, windows, lighting, machineries heat gains schedule, as
well as the buildings users’ occupation and activity are simulated by means of the Type 56. TRNSYS is also used
to accurately model all of the plant components. The work also includes comprehensive energy, environmental
and economic analyses to maximize the plants profitability, evaluated by considering both operating and capital
costs. Sensitivity analyses aiming at establishing the optimal values of the most important design parameters are
also performed. The developed plants achieve important savings in terms of carbon dioxide emissions due to the
use of renewable energy sources and the high efficiency of the included technologies. The best economic indexes
are obtained for the layout using electricity-driven technologies, resulting in very profitable operation with a
payback period of about 6.2 years.

1. Introduction inaccessible communities (medium or small islands) providing space
heating and cooling, electricity, and desalinated water in a single
Renewable polygeneration systems are becoming increasingly at- system. This combination allows one to optimize the use of energy
tractive in the transition toward a zero-carbon society expected by cascades (heat and/or electricity) for freshwater production. For remote
2050. Polygeneration plants play a key role in the energy-water nexus islands, characterized by a large availability of seawater, abundant re-
since the integration of different energy and water technologies in the newable energy sources, and limited availability of conventional fossil
same facility allows one to maximize the system efficiency. In parti- fuels and fresh water, the concept of polygeneration is a very attractive
cular, polygeneration systems represent a key solution for remote and option [1].

⁎ Corresponding author.
E-mail addresses: francesco.calise@unina.it (F. Calise), francescoliberato.cappiello@unina.it (F.L. Cappiello), maria.vicidomini@unina.it (M. Vicidomini),
fpetrako@ing.uc3m.es (F. Petrakopoulou-Robinson).
https://doi.org/10.1016/j.enconman.2020.113043
Received 25 March 2020; Received in revised form 28 May 2020; Accepted 29 May 2020
Available online 12 June 2020
0196-8904/ © 2020 Elsevier Ltd. All rights reserved.