Polygeneration and advanced energy

systemsProject on SOFC system for a multi-family

household

Rosa De Maio

Alberto Gaeta

Matteo Pizzicotti

Calogero Andrea Savaia

Household Selection and loads

calculationMULTI-FAMILY HOUSEHOLD

Located in Turin, Italy

4 flats

Each flat has an area of 100 m2

LOADS CALCULATION→ according to the standard “VDI 4655” from Germany

CONSUMPTION LOADS [kWh/day] LOADS [kWh/year]

Electrical Energy 32,9 12000

Heating Energy 120,5 44000

DHW Energy 11,0 4000

Household Selection and loads calculation

Tipical day profiles:

0

0.5

1

1.5

2

2.5

3

0 20 40 60 80 100

[kW

]

Time [15 min]

Electrical load profile [kW]

0

2

4

6

8

10

12

0 10 20 30 40 50 60 70 80 90 100

[kW

]

Time [15 min]

Thermal heating load profile [kW]

0

0.5

1

1.5

2

2.5

3

3.5

0 20 40 60 80 100

[kW

]

Time [15 min]

DHW thermal load profile [kW]

Sizing of the SOFC and system layout

designTo find the optimal size, an Aspen Model of the SOFC system has been realized,

and 3 different simulations have been performed.

THERMODYNAMIC VALUE SIM . 1 – 1 kW SIM . 2 – 1,5 kW SIM . 3 – 2 kW

Gross Electrical Power [W] 1000 1500 2000

NG Consumption [kg/s] 3,39E-05 5,09E-05 6,79E-05

Thermal Recovery [W] 469,8 705,5 940,5

Blower 1 (NG) power [W] 1,3 2,0 2,7

Blower 2 (AIR) power [W] 29,7 44,7 59,5

Net Electrical Power[W] 969,0 1453,4 1937,9

Electrical efficiency [%] 0,53 0,53 0,53

Thermal efficiency [%] 0,26 0,26 0,26

Difficulties of SOFC in following instantaneously the requested load

The aim of the system is to auto-produce the internal energy request

SOFC has an estimated life of 14 years

The SOFC sizes have been chosen following these hypothesis:

Thermal energy:

The thermal energy recovered is always too low to cover entirely the energy request, so

it is necessary to integrate the thermal production with a boiler of 12 kW

Economic Analysis

• SOFC COMPONENTS COST

FUEL CELL 10.000 €/kW

SYSTEM FC cost [€]Boiler cost

[€]Additional cost [€] Total investment cost [€]

Fuel Cell (1 kW) + Boiler 10000 1200 392 11592

Fuel Cell (1,5 kW) + Boiler 15000 1200 567 16767

Fuel Cell (2 kW) + Boiler 20000 1200 742 21942

STACK (changed every 5 years) 30% of the SOFC cost

BOILER (η=90%) 100 €/kW

ADDITIONAL COSTS 3,5% of total investment

Economic Analysis

• ELECTRICITY AND NATURAL GAS COST

Base cost

[€/kWh]“Imposta Erariale” [€/kWh]

IVA 10%

[€/kWh]Total electrical energy cost [€/kWh]

0,161336 0,00908 0,017042 0,1874576

ELECTRICITY

Price of electrical energy without taxes

for the reference year 2017

NATURAL GAS

Base cost

[€/Sm3]Duty [€/Sm3] “Addizionale regionale” [€/Sm3]

IVA

[€/Sm3]

Total NG cost

[€/Sm3]

Boiler 0,399913 0,186 0,0258 0,134576 0,746290

FC 0,399913 0,186 0,000134 0,058605 0,644653

The excess of electricity is sold to the grid with a price of 0,039 €/kWh.

Basic price of natural

gas without duties,

published by GSE

Economic Analysis• TOTAL ANNUAL ENERGY COST

Electrical energy

From Grid To Grid

Energy [kWh] Annual cost [€/y] Energy [kWh] Annual revenue [€/y] Total annual cost [€/y]

Fuel Cell [1 kW] + Boiler 3511,7 652,26 0,0 0,00 652,26

Fuel Cell [1,5 kW] + Boiler 1127,5 209,42 1858,9 66,58 142,84

Fuel Cell [2 kW] + Boiler 359,2 66,72 5334,8 191,08 -124,36

Natural gasFuel cell Boiler

Consumption [Sm3] Annual cost [€/y] Consumption [Sm3] Annual cost [€/y]Total annual cost

[€/y]

Fuel Cell [1 kW] + Boiler 1581,6 1019,59 4849,1 3618,82 4638,41

Fuel Cell [1,5 kW] + Boiler 2373,6 1530,12 4620,9 3448,56 4978,67

Fuel Cell [2 kW] + Boiler 3164,4 2039,91 4393,5 3278,85 5318,76

Economic Analysis

• CASH FLOW ANALYSIS

Cumulated cash flow alwaysnegative for SOFC

• initial investment is high;

• every 5 years there is the

necessity to replace the stack;

• overproduced electricity is sold

at a too low price.

It’s useful a comparative analysis between SOFC and boiler-only cases

The annual cost of energy for the boiler-only case is 6187 €

Economic Analysis

The cumulated cash flow of the Fuel Cell is always below that of the boiler

case.

• investment cost for the SOFC is extremely

high;

• operational cost for SOFC is slightly lower

than the boiler-only case;

• every 5 years the difference between the

two cumulated increases;

• selling price is much smaller than the

purchasing one.

• COMPARATIVE ANALYSIS OF SOFC AND BOILER

Economic Analysis

• COMPARATIVE ANALYSIS OF THREE SIZES OF SOFC AND BOILER

Without any subsidies

the gap, with respect to

the boiler-only case,

grows as size of SOFC

increases

The best solution seems to be the boiler-only case

Subsidies• MAKING SOFC COMPETITIVE TECHNOLOGIES

• Subsidies for reduction of operational costs

Earnings from the production of electricity

► In Italy there are not subsidies for fuel cells

As example of subsidy → “Conto Energia” for photovoltaic systems

Chosen “Quinto Conto Energia” (the most recent) :

electricity produced by SOFC for auto-consumption is rewarded with 0,10 €/kWh;

electricity in excess is sent to the grid and gives an equivalent credit of energy.

Subsidies• COMPARATIVE ANALYSIS OF THREE SIZES OF SOFC AND BOILER WITH

SUBSIDY

The cumulated cashflow of the SOFC,after 11-13 years isabove that of theboiler-only caseTime to reach break-even point increaseswith the size of theSOFC, so the moreconvenient solution isthat of 1 kW

Conclusions► Now, the SOFC is a technology in development and still it is not competitive with other

solutions:• The capital costs are still too high and are not compensated by much lower operational costs;

• Need of changing the stack every 5 years;

• Analysis is limited by the fact that:

the total load is considered uniformly split in the entire year with a typical daily profile;

the cost of electricity has been considered constant for all the years of operation of the system.

• can generate a reduction of the investment price and/or a higher income for production;

• can help the diffusion and as a consequence the development of this technology

►In the future, the introduction of subsidies for SOFC:

Thanks for yourattention!