Chapter2: Economics & Energy from Waste

Question 1

Give the methods to determine the economic efficiency of an arbitrary investment

Answer 1

1. Capital value method: Calculate 𝑁𝑃𝑉
2. Annuity method: Calculate 𝐴𝑁 from 𝑁𝑃𝑉
3. Interest rate methods: Calculate 𝑧 for 𝑁𝑃𝑉 = 0 (internal rate of return)
4. Amortization period: Calculate 𝑇 for 𝑁𝑃𝑉 = 0

Question 2

How do consumer price correlate with unemployment?

Answer 2

1. Consumer price index correlates with wages and salary
2. Wages and salary is following GDP/capita with a time lag and is hardly negative
3. Unemloyment rate correlates with GDP/capita

Question 3

A representative shopping cart costs 150 € today. How much costs the same amount of goods in the future, at a constant inflation rate of 2.5 % per year (I) and a variable inflation rate of 2.5 % per year (II)

Answer 3

Calculation with constant inflation rate: 𝐴_𝑖 = 𝐴₀ ⋅ 𝑞_𝑖

Calculation with variable inflation rate: 𝐴_𝑖+1 = 𝐴_𝑖 ⋅ 𝑞_𝑖

Question 4

What is the Net present value (NPV)?

Answer 4

The net present value gives the actual value for a series of constant future payments:

𝐴𝑖 Periodic payment

𝑁𝑃𝑉 Net present value (at 𝑡 = 0)

𝑏 Present value factor

𝑧 Discount rate/Interest rate

𝑇 Period under review

𝑞 Discount factor

Question 5

Example: A pension fund with a monthly payment of 300 €/month and a time span of 40 years, Assuming a discount factor of 2.5 % being equivalent to the average inflation

Answer 5

Question 6

What is The annuity 𝐴N

Answer 6

𝑁 is the annual payment in a period 𝑇, which is necessary to justify an investment.

Question 7

Price-dynamic payment sequences? and how are they derived?

Answer 7

A price-dynamic payment sequence considers interest rates (𝑧 or 𝑞) and price change factors (𝑗 or 𝑟) for materials. Based on this a net present value can be calculated.

slides 13-17

Question 8

Replacement value of investments

Calculate the net present value and terminal value of a building. Calculate the replacement values of blocktype CHP and the annuities. What is the effect of repairs?

Answer 8

Question 9

Give again an overview of the following basic economic parameters:

-Annuity factor

-Net present value factor

-Price dynamic present value factor

-Matching coefficient for replacements

-Net present value

-Net present value of replacements

Answer 9

Question 10

Right down the formula of a cost function and explain Why do cost functions have high uncertainties?

Answer 10

Cost functions can be used for specific components. They depend on a characteristic parameter 𝑋 and are referred to a reference component (index 0)

Z₁/Z₀= (X₁/X₀)ⁿ

Question 11

What characteristics do small systems and modular systems have? Draw the corresponding curves!

Answer 11

• Small systems can make use of cheap components (off-the-shelf products)
• Stack systems can increase part load behaviour and decrease shutdown periods due to maintenance.

Question 12

What are the most expensive, and cheapest energy systems in terms of specific investment costs?

Answer 12

Question 13

How does the cost structure differ from one power generation system to another?

Answer 13

Investment costs vs fuel costs

variable costs vs fixed costs

Gas Turbine with exhaust gas cleaning (EGC)

Question 14

Electricity generation costs

Answer 14

1. Electricity Generation Costs are shown in dependence of full load hours for all plant types.
2. Note, that Flh for Wind and PV cannot be controlled. EGC are determined externally.
3. Note, that Wind (on) and PV have identical curves!

• 1. CC is more economic than other fossil fuels for Flh<1200 h/a
• 2. Typical Flh for PV: Flh~1100 h/a
• 3. Typical Flh for wind (on): Flh~1650 h/a
• 4. Typical Flh for wind (off): Flh~4450 h/a

Question 15

What waste in Germany gets recovered, and which gets recycled?

Answer 15

• Residual waste –> Bio-mechanical (5 Mio t/a) Waste incineration (19 Mio t/a)
• Food/Biodegradable –> Composting Fermentation plant Biomass plant

–> Both get Recovered (Energy | Fertilizer)!

• Paper
• Glas/Plastics/Tin
• Batteries (Supermarket, Grocery store, Drugstore)
• Electrical devices (Municipal return station)
• Clothing
• CDs

–> All these get Recycled!

Question 16

Describe the waste hierarchy from most favored to least favord option!

Answer 16

Prevention–> Re-Use–>Recycling–> Other recovery ( For ex: Engery recovery)–> Disposal

Question 17

How is Germany doing in recycling compared to other euro countries?

Answer 17

Question 18

From which sector does the waste in Germany mostly come from?

Answer 18

Overall waste has been reduced and is on almost constant level since 2004

Reduction has been achieved in Building and demolition sector

• Municipal solid waste on constant level
• Rubble is reduced due to phase out of coal mining
• Production and trade has increased

Question 19

Name all the steps of a waste plant (EfW)
NB: don’t take this question so seriously xD!

Answer 19

Question 20

Composition of waste

Answer 20

• water content
• heating value

Question 21

What should be considered in the design of an EfW-plant? and what technology is used in the EFW?

Answer 21

• Reference fuel is design criteria
• Lower heating values make preheating necessary
• Higher heating values damage the grate firing and lead to slagging

Grate firing technology

• Combustion temperature: 1200 °C
• Cladding in combustion chamber supports ignition
• Two-stage air firing: Primary air for gasification on grate and secondary air for afterburning
• Typical load: 1-1.5 MWth/m² (length is fixed for fuel conversion, width determines the load)
• Upper load limit: 100 MWth (Limit for homogeneous fuel feeding) Residence time in first pass 2s @ 850 °C (Destruction of dioxins)

Question 22

Where do energy losses come from in the EfW?

Answer 22

• Boiler
• Cycle losses
• Gear losses
• Generator losses
• (Parasitic power almost 20%)

Question 23

How can we increase boiler efficiency?

Answer 23

Increase of boiler efficiency can be obtained by

• reduction of flue gas outlet temperature. BUT: Acid dew point constraints the exit temperature of the flue gas to 180 °C.
• increase of combustion temperature BUT: Combustion temperature is limited by grate firing to <1200 °C (further limitation from ash)

Question 24

How can we avoid chlorine induced corrosion?

Answer 24

–> High flue gas and wall temperatures need to be avoided due to chlorine induced corrosion. This limits combustion temperature and thermodynamic efficiency (by live steam parameters)

Question 25

Name all the following components:

Answer 25

Question 26

What are the air polluters types in Germany?

Answer 26

1. NOx 2886
2. NH3 792,4
3. NMVOC 3113
4. SO2 5307
5. Dust 1933
6. PM10₁₉₉₅ 313
7. PM2.5₁₉₉₅ 191
8. CO 12582

Fine dust: PM10 is the cumulated mass of particles with diameters smaller than 10 µm. PM2.5 is the cumulated mass of particles with diameters smaller than 2.5 µm

Question 27

What are the two types of poulltant emissions?

Answer 27

Gaseous and particulate

Question 28

Which is the sector the most polluting in Germany?

Answer 28

 Energy sector is dominating the air pollutant emissions (only exeptions are: NMVOC, NH3, TSP

Question 29

What is the state of art of emission control?

Answer 29

Question 30

What are the Types of payment for EfW-Plants:

Answer 30

• Capital-linked payments: Depend on the total investments and include periodic payments for repairs and maintenance.
• Consumption-linked payments: Consumption of energy and other materials (e.g. for lubrication, gas cleaning, water)
• Operation-linked payments: Part payments for e.g. operation, cleaning, service and inspection. They can be determined as individual amounts or dependent on the investments)
• Other payments: Costs for insurance, taxes and general expenses (e.g. office stuff). NO profits and losses are to be included
• Lodgement: Earnings Change rates: Changes in costs due to unforeseen

Question 31

What do investments costs depend on?

Answer 31

Investment costs depend on:

• Size
• Location and existing infrastructure
• Equipment and technology
• Energy utilisation

Question 32

What do investments costs cover?

Answer 32

• Capital-related costs  Plant components, Buildings, Infrastructure
• Requirement (consumption)-related costs  Operating supplies, auxiliary energy
• Operation-related costs  Repairs, service, inspection, staff
• Other costs  Insurance, administration and management

Question 33

What do costs of incineration depend on?

Answer 33

• Firing technology
• Age of plant
• Efficiency of power generation
• Heat extraction to district heating system
• Economic constraints (e.g. interest rates applied)

Difference of waste collection and disposal fee includes also the waste collection system.

Question 34

What criteria should be considered in the sensitivity study of waste recovery costs?

Answer 34

• Heating value of waste determines the throughput of waste per year. With increasing heating value, the waste recovery costs increase most.
• Heat extraction into a district heating system has also significant effect on the waste recovery costs.
• Electricity production or electricity price have only moderate influence. However, it is desired from the ecologic point of view.