Chapter2: Economics & Energy from Waste Flashcards
Give the methods to determine the economic efficiency of an arbitrary investment
- Capital value method: Calculate πππ
- Annuity method: Calculate π΄π from πππ
- Interest rate methods: Calculate π§ for πππ = 0 (internal rate of return)
- Amortization period: Calculate π for πππ = 0
How do consumer price correlate with unemployment?
- Consumer price index correlates with wages and salary
- Wages and salary is following GDP/capita with a time lag and is hardly negative
- Unemloyment rate correlates with GDP/capita
A representative shopping cart costs 150 β¬ 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)
Calculation with constant inflation rate: π΄π = π΄0 β ππ
Calculation with variable inflation rate: π΄π+1 = π΄π β ππ
What is the Net present value (NPV)?
The net present value gives the actual value for a series of constant future payments:
π΄π Periodic payment
πππ Net present value (at π‘ = 0)
π Present value factor
π§ Discount rate/Interest rate
π Period under review
π Discount factor
Example: A pension fund with a monthly payment of 300 β¬/month and a time span of 40 years, Assuming a discount factor of 2.5 % being equivalent to the average inflation
What is The annuity π΄N
π is the annual payment in a period π, which is necessary to justify an investment.
Price-dynamic payment sequences? and how are they derived?
A price-dynamic payment sequence considers interest rates (π§ or π) and price change factors (π or π) for materials. Based on this a net present value can be calculated.
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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?
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
Right down the formula of a cost function and explain Why do cost functions have high uncertainties?
Cost functions can be used for specific components. They depend on a characteristic parameter π and are referred to a reference component (index 0)
Z1/Z0= (X1/X0)n
What characteristics do small systems and modular systems have? Draw the corresponding curves!
- 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.
What are the most expensive, and cheapest energy systems in terms of specific investment costs?
How does the cost structure differ from one power generation system to another?
Investment costs vs fuel costs
variable costs vs fixed costs
Gas Turbine with exhaust gas cleaning (EGC)
Electricity generation costs
- Electricity Generation Costs are shown in dependence of full load hours for all plant types.
- Note, that Flh for Wind and PV cannot be controlled. EGC are determined externally.
- Note, that Wind (on) and PV have identical curves!
- CC is more economic than other fossil fuels for Flh<1200 h/a
- Typical Flh for PV: Flh~1100 h/a
- Typical Flh for wind (on): Flh~1650 h/a
- Typical Flh for wind (off): Flh~4450 h/a
What waste in Germany gets recovered, and which gets recycled?
- Residual waste β> Bio-mechanical (5 Mio t/a) Waste incineration (19 Mio t/a)
- Food/Biodegradable β> Composting Fermentation plant Biomass plant
β> Both get Recovered (Energy | Fertilizer)!
- Paper
- Glas/Plastics/Tin
- Batteries (Supermarket, Grocery store, Drugstore)
- Electrical devices (Municipal return station)
- Clothing
- CDs
β> All these get Recycled!
Describe the waste hierarchy from most favored to least favord option!
Preventionβ> Re-Useβ>Recyclingβ> Other recovery ( For ex: Engery recovery)β> Disposal
How is Germany doing in recycling compared to other euro countries?
From which sector does the waste in Germany mostly come from?
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
Name all the steps of a waste plant (EfW)
NB: donβt take this question so seriously xD!
Composition of waste
- water content
- heating value
What should be considered in the design of an EfW-plant? and what technology is used in the EFW?
- 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 Β°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/mΒ² (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 Β°C (Destruction of dioxins)
Where do energy losses come from in the EfW?
- Boiler
- Cycle losses
- Gear losses
- Generator losses
- (Parasitic power almost 20%)
How can we increase boiler efficiency?
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 Β°C.
- increase of combustion temperature BUT: Combustion temperature is limited by grate firing to <1200 Β°C (further limitation from ash)
How can we avoid chlorine induced corrosion?
β> 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)
