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Tools for a sustainable development - The thermodynamic conversion of solar energy by innovative heat engines.



The presentation was discussed in a conference organized by "B+LabNet", at the University of Brescia: Environment, Health, Sustainability, June 5th 2019.
The thermodynamic conversion of solar energy by
innovative heat engines
-Tools for a sustainable development
affordable and clean energy sustainable cities and communities climate
G. Di Marcoberardino, C. Invernizzi, P. Iora
The Sun: a primary energy source, I
Sun, although in an indirect way, is responsible for the greater
part of the different renewableenergy sources on the earth,
and it can so be considered and classified as a primary energy
The energy from the Sun is the result of specific nuclear fusion reactions:
hydrogen is converted into helium, that, in its turn, ageing the star, is
converted in heavy nuclides. When the mass number of the products reach
a value about 60 (iron and nikel) the fusion reactions stop … in some
billions of years
Convegno «Ambiente, Salute e Sostenibilità» 5 giugno 2019
The Sun: a primary energy source, II
The heat produced by the nuclear reactions keeps the core
temperature at several millions degrees.
The high temperature sustains the fusion reactions and the produced
energy is then transferred on the surface and irradiated into the outer
For a terrestrial observer, the Sun
looks like:
oa black body with a temperature of
≈ 6000 degrees and,
owith a thermodynamic availability of
≈ 0.93
oAverage distance sun – earth: ≈ 150
x 106 km
oSun diameter: ≈ 1.5 x 106 km
oEarth diameter: ≈ 1.3 x 104 km
oSolar constant: 1367 W/m2
The Sun: the available energy, I
Potentially, the energy from the Sun is
unlimited. But,
(1) The solar radiation is very diluted,
intermittent and not uniformly distributed;
(2) At the Earth level the collected energy
depends on the inclination and on the
orientation of the surface and on the year
season too.
The Sun: the available energy, II
- b = 0°e g= 0°: 1370
kWh/m2year (= 100)
- q = 0° (tracking
surface about two
axes): 2181 kWh/m2
The “solar thermodynamic”
The thermodynamic conversion of the solar energy
The thermodynamic conversion of the solar energy in electric
energy takes place, in sequence, by:
• the collection of the solar radiation as heat on surfaces with a
high absorption coefficient at the highest possible temperature;
transferring the heat to a lower temperature heat sink (usually
the environment) by means of a thermodynamic cycle -a heat
engine -producing mechanical energy.
The first HT solar engines in
Augustin Mouchot (7 April 1825 – 4 October
1912): 1860 - << … coal will undoubtedly be
used up. What will industry do then? … Reap
the rays of the Sun! >>
The solar powered printing press of
Abel Pifre, August 6th 1882. While
exhibiting it at the Gardens of the
Tuileries, he printed five hundred
copies of the Le Journal de Soleil (a
journal specially composed for the
Abel Pifre (1852 -
1928) an engineer, an
assistant and a
collaborator to Mouchot.
The first HT air solar engines in America
John Ericsson (July 31, 1803 – March 8, 1889)
1872 rappresentazione
del -primo -motore ad
aria con concentratore
1884 concentratore
Nature, August 2, 1888, p. 319
Ericsson felt he could not << recommend the
erection of solar engines in places where there is
not steady sunshine until means shall have been
devised for storing up the radiant energy in such
a manner that regular power may be obtained
from irregular solar radiation >>. From J. Perlin,
Let it Shine, New World Library, 2013, p. 106
The first practical solar engine in Al Meadi
Egypt, 1912
55 HP (≈ 40 kW) of power, enough
to pump 6000 gallon of water per
minute (≈ 23 m3/min). 200 square
feet/HP collector area (≈ 25
Frank Schuman (1862 -1918) and Charles
Vernon Boys (1855 1944)
The LT “solar thermodynamic” in Italy 1920-1960
Tito Romagnoli
between 1923 and
1930 built a series of engines (of
small power, 2 HP (1.5 kW), and
low efficiency).
Luigi d’Amelio
(1893-1967), in 1935,
designd a turbine solar engine.
Daniele Gasperini
(1865 -1960) e
Ferruccio Parri
(1897 1980) in 1955,
at the fair of the Solar Energy in
Phoenix (USA), presented their “solar
pump SOMOR”.
The LT “solar thermodynamic” in Italy 1970-1980
§Facchini U., Motori solari per l’agricoltura, La Termotecnica, No. 5 (1979), 292-
§Angelino G., Facchini U., Gaia M., Macchi E., Sassi G. Motore solare della
potenza di 3 kW per il pompaggio di acqua – Programma e stato dei lavori,
Condizionamento dell’aria, Riscaldamento, Refrigerazione, No 11 (1977), 884-
§Gaia M., Macchi E., A comparison between Sun and Wind as Energy Sources in
Irrigation Plants. In: Proceedings of International Solar Eneregy Society (ISES)
Congress, Delhi (India), January 1978. Vol I, 265-272.
§Macciò C., Tomei G., Angelino G., Gaia M., Macchi E. Operational Experience of a 3.0 kW Solar
Powered Water Pump. In: 1979 Silver Jubilee International Congress of the International Solar
Energy Society (ISES), May 28 – June 1, Atlanta, Georgia (USA): Sun II, Vol 2, pp 1501-1505,
Pergamon Press.
§Gaia M., Angelino G., Macchi E., De Heering D., Fabry J. P. Risultati sperimentali del motore a
fluido organico sviluppato per l’impianto solare di Borj Cedria. energie alternative HTE anno 6 no
27, gennaio-febbraio 1984, 31-34.
§Angelino G., Gaia M., Macchi E., Barutti A., Macciò C., Tomei G. Test Results of a Medium
Tem pera ture Sol ar E ngi n e, International Journal of Ambient Energy, July 1982, Vol. 3, No. 3, pp.
The opportunity to concentrate the solar energy
Greater concentration ratio
Higher temperatures
High efficiency
Lower electricity
production costs
The solar power tower plants, I
The solar plants PS10 (Planta Solar 10) and
PS20 (Planta Solar 20) in Sanlucar la Mayor
vicino Seville, Andalusia, Spagna. 1255
collectors, ● 80 hectares ● Nominal power 20
MW ● capacity factor 27%, ● Net energy 48
The solar power tower plants, II
The plant scheme – simplified – of the
traditional solar power tower plants.
The steam cycle (the “power block”) – simplified
– of the traditional solar power tower plants.
The “SCARABEUS” project, I
SCARABEUS: Supercritical CARbon dioxide/Alternative fluids
Blends for Efficiency Upgrade of Solar power plants
The Concentrated Solar Power (CSP) plants have currently a Levelized Cost of
Electricity (LCoE) of about 150 €/MWh, still far from the level targeted (100 €/MWh), except
for few installations in exceptionally good locations.
A way pursued today to reduce the electricity cost is to resort to thermodynamic cycles with carbon
dioxide (CO2) instead of steam as working fluid.
But, carbon dioxide (a gas, at ambient pressure and temperature), does not allow the recourse to
the condensation(*) in locations where the air temperature is greater than 30 °C.
(*) The condensation – when possible – improves noticeably the
useful power and the efficiency of the heat engine.
The “SCARABEUS” project, II
”power block” and turbines
dimensions for
thermodynamic cycles with
steam and carbon dioxide.
The aim of the project is to
develop ● an innovative
thermodynamic cycle using
blends of CO2, thus improving
the efficiency from the current
42% to over 50%, and to
demonstrate ● a reduction of
the capital costs (CAPEX) of
30%, and of the operating
costs (OPEX) of 35% with
respect to state-of-the-art
steam cycles and exceeding
the reduction achievable with
standard supercritical CO2
The “SCARABEUS” project, III
Academia and R&D
di Milano (IT)
Exergy (IT)
di Brescia(*) (IT)
University of Seville (ES)
City University of London (UK)
Vienna University of Technology (AT)
It is a project of 48 months, started in April 2019 and it will continue until March
Coordinator: Politecnico di Milano.
The project is founded by the European Uninion’s Horizon 2020 research and
innovation programme, under grant agreement n. 814985.
(*) at the Università di Brescia is assigned the WP2: CO2Blend Development
The “SCARABEUS” project, IV
Determine the most promising fluid for blending the CO2
Assess the thermodynamic properties of the blended CO2in terms of critical curve and their
stability up to 700 °C
Demonstrate the thermal stability of the two CO2blends for 2000 hours
Stable at high T?
Good properties?
The “SCARABEUS” project, V
Personale coinvolto
Full professor of Energy Systems
Head of ERGO’s group and Fluid Test Lab
Research interests: Organic Rankine Cycles, thermodynamics of working pure
fluid and mixtures, modeling and optimization of advanced power cycles
Full professor of Energy Systems
Member of ERGO group and GECOS (Milan)
Research interests: advanced power cycles, fuel cells modeling, electric vehicles
Phd candidate
Graduated in Mechanical Engineering from
Capital University of Science and Technology
Research interests: Thermodynamics of mixtures
for closed power cycle
Many years laboratory
experience in thermal stability
Highly skilled in finding circuit
leakages and fixing them.
Assistant professor since November 2018
Phd Politecnico di Milano
Research interests: advanced power cycles,
fuel cells modeling, experimental analysis
The “SCARABEUS” project, VI
Thermal stability test procedure
The thermal stability of the CO2blends need to be experimentally verified.
The method we adopt, is based on the analysis of the deviations in the vapor
pressure curve of the fluid after subjecting it to thermal stress tests at
increasing temperature according to the following procedure:
(a) loading the sample fluid in the test circuit
(b) evaluation of the reference vapor pressure of the virgin fluid
(c) thermal stress test in a furnace
(d) measurement of the vapour pressure curve and comparison to the
reference value
Thermal stability test facility
(1,2) muffle furnace for stress tests, (3)
helium bottle for leakege test, (4)
thermostatic bath [-40°C,50°C] where the
saturation pressure curve is measured, (5)
Data Acquisition System to record T and p
during the tests
The “SCARABEUS” project, VII
What’s a stable fluid?
Many factors can
influence the thermal
stability of a working
fluid, such as the
materials and the
presence of
contaminants. Thus,
in a power plant, it is
important to select the
proper materials
particularly for the
high temperature
Thermal stress analysis of CO2in stainless steel at
500 °C. Clear sign of decomposition can be
The “SCARABEUS” project, VIII
● Liquid phase at T = 50
°C benefits in terms of
reduction of the
compression work.
●The resulting power cycle
based on the TiCl4-CO2
mixture may have higher
efficiency than that with
pure CO2as working fluid.
T-S diagram at different compositions of the the TiCl4-CO2
mixture, resulting in different critical temperatures and in
different thermodynamic properties.
An example: a mixture of
carbon dioxide (CO2) and
titanium tetrachloride (TiCl4)
The “SCARABEUS” project, IX
Heater: thermo-chemical
compatibility of the
working fluid with the
materials Mechanical
properties of materials
Some technological challenges
Turbine: fluid-dynamic
design and optimization
Recuperator: mechanical
design, thermal
effectiveness Thermal
and pressure-drop design
Condenser: mechanical
design, thermal
effectiveness Thermal
and pressure-drop design
The properties of the
working fluid
Supercritical CARbon dioxide/Alternative fluids Blends for Efficiency Upgrade of Solar
power plant
The SCARABEUS project has received funding from the
European Union’s Horizon 2020 research and innovation
programme under grant agreement814985
Ambiente, Salute e Sostenibilità
Secondo Convegno organizzato dal Laboratorio B+LabNet in occasione della
Giornata Mondiale dell’Ambiente e del Festival dello Sviluppo Sostenible 2019
June 5th 2019
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