Post on 02-Aug-2015
Case Study Project
District Heating Network and Heat Storage
Renewable Energy City Ortenberg
WS 2012/2013
District Heating Network & Storage - i - Anders, Gerami, Hussein
Abstract
Authors: Anders, Gerami, Hussein
Advisor(s): Prof. Dr. P. Treffinger, Prof. Dr. J. Pfafferott
Semester: WS 2012/2013
Subject: Case Study (Calculations for District Heating Network and Heat Storage
for Renewable Energy City Project in Ortenberg including solar thermal gain).
Contents: The main task that was delegated to us was to perform a complete
design and calculations for a district heating network to deliver both space heating
and DHW demand for the people in Renewable Energy City Project in Ortenberg.
This report should summarize the final work done at the final phase of the
Renewable Energy City project in Ortenberg. It should also show the key parameters
and assumptions done during the design. Along with the excel sheet handled to the
supervisors, this paper should be able to deliver a clear view on all the calculations,
strategy and methodology adopted throughout all the design phase.
District Heating Network & Storage - ii - Anders, Gerami, Hussein
Foreword
In coherence with the work required and done throughout all the different phases of
this project, the project of Renewable Energy City to feed the small city of Ortenberg
with clean and renewable energy was a top notch in renewable energies utilization
and deployment strategies. The motivations were obtained from our passion to
realize our academic experience in the field of renewable energies to an applicable
live project.
Anders, Gerami, Hussein Offenburg, January 23, 2013
District Heating Network & Storage - iii - Anders, Gerami, Hussein
Table of Contents
Abstract .................................................................................................................... i
Foreword ................................................................................................................. ii
Table of Contents................................................................................................... iii
List of Figures and Illustrations ............................................................................ iv
List of Tables .......................................................................................................... iv
1 Introduction ....................................................................................................... 1
2 District Heating and DHW ................................................................................. 2
3 Location of the District Heating Utility and the Areas .................................... 4
4 Connection to Solar Collectors ........................................................................ 7
5 Thermal Storage ................................................................................................ 8
6 Pipes and branches ........................................................................................ 10
7 Pumps .............................................................................................................. 12
7.1 Applications................................................................................................ 12
7.2 Features and benefits ................................................................................ 12
8 Equipping the Grid .......................................................................................... 14
9 Operation and Maintenance ........................................................................... 15
Attachment .............................................................................................................. a
District Heating Network & Storage - iv - Anders, Gerami, Hussein
List of Figures and Illustrations
Figure 1: Regarding facts in the heat distribution network ......................................... 1
Figure 2: District Heating Network Layout ................................................................. 2
Figure 3: Sankey-Diagram Ortenberg ....................................................................... 3
Figure 4: Ortenberg with location of the thermal storage ........................................... 5
Figure 5: Ortenberg split up in six areas .................................................................... 6
Figure 6: District Heating Network P&ID ................................................................... 7
Figure 7: Water Storage Tank ................................................................................... 9
Figure 8: Heating grid with storage and pumps ....................................................... 10
Figure 9: District Heating Pump .............................................................................. 13
Figure 10: Project PF Diagram ................................................................................ 14
Figure 11: Installed units and costs ......................................................................... 15
Figure 11: Variable costs ........................................................................................ 15
List of Tables
Table 1: Properties areas Ortenberg ......................................................................... 6
Table 2: Tank Assorted Costs ................................................................................... 9
Table 3: District Heating pipe properties ................................................................. 11
Table 4: Solar thermal pipe properties ................ Fehler! Textmarke nicht definiert.
Table 5: Pumps for main branches ......................................................................... 13
Table 6: Costs for pumps ........................................................................................ 13
District Heating Network & Storage - 1 - Anders, Gerami, Hussein
1 Introduction
Our work as Group 1 in this Case Study was delegated different tasks, beginning
from the 1st phase and ending with the 3rd, we were able to gain a better overview on
the liaison between different systems that were involved in designing a Clean Energy
Village. As we have approached with the calculation of the Energy (Electricity and
Heat) from the Biogas potential in the city of Ortenberg, we were able to get a better
overview about the input, recycling, processing and conversion of the raw
biodegradable materials into useful energy. Since our final task was to design the hot
water grid for the district heating project, we some affordable and simple techniques
to deliver an approximated image on how to design a district heating grid based on
the available information provided by other groups.
Figure 1: Regarding facts in the heat distribution network
District Heating Network & Storage - 2 - Anders, Gerami, Hussein
2 District Heating and DHW
A lot of parameters have been set in the third phase as constraints for our group to
start working from. As it was set from the beginning, that only 65% of the total
households will be supplied with heat energy, our calculations were mainly based on
this constraint. Our decision to utilize an open district heating connection was based
on its advantages which are:
Figure 2: District Heating Network Layout
The scheme requires neither heat exchangers nor circulation pumps, so the
money invested for the equipment preparing for the DWH is not needed.
The direct connection to the grid means that the heating water in the grid
pipes will circulate in the radiator networks inside each home, which will make
our calculations for the heat losses much easier by using only one
temperature difference.
District Heating Network & Storage - 3 - Anders, Gerami, Hussein
The hot water circuit can be easily illustrated by a Sankey-Diagram. The diagram for
this project is shown in Figure 3.
Figure 3: Sankey-Diagram Ortenberg
District Heating Network & Storage - 4 - Anders, Gerami, Hussein
As we have experienced a shortage in both topographical and geographical
conditions and descriptions for Ortenberg, Google Earth© was very helping tool in
determining the urban density in almost equally 6 divided zones (see chapter 3).
Therefore, the number of houses per each zone has been calculated using a sharing
ratio in percentages.
The total heat demand (65% of the total), has been distributed according to the
share of each area of the total households area and both the volume low rates and
velocities have been calculated using the basic heat transfer equations used in the
excel sheet. By fixing the velocity of 2 m/s, the sizes of the pipes were calculated with
the help of the flow rates and approximated to the closer DN values according to the
German standards. The insulation for the pipes have been recognized according to
the outer surface area and length (pipe volume) of the pipe and simply multiplied by
the cost/m3. Finally the total costs of investment have been calculated with
coherence with the pipe materials, insulation materials, mounting materials and
maintenance cost.
3 Location of the District Heating Utility and the
Areas
In order to ensure an appropriate delivery of heat to the amount of connected
households to the grid, we had to determine a place to erect and operate the thermal
storage and therefore the connection to the heating grid.
The deciding factors are
- central position to ensure a short length of the pipes
- connection to open land to have a short way to the CHP
- minimize optical disturbance
District Heating Network & Storage - 5 - Anders, Gerami, Hussein
Figure 4: Ortenberg with location of the thermal storage
As you see in Figure 2, we agreed on the marked location because of the mainly
central position and the direction towards west (in order to prevent a connection to
the storage from the CHP over the hills aside).
The goal to provide 65 % of the overall heat demand households with heat will be
realized by splitting up the hot water stream coming from the storage and distributing
the heat star-shaped net.
As mentioned in chapter 2, the stream is split up in 3 main branches, marked as
line 1, line 2 and main_line (providing area 3, 4, 5 and 6).
You can see in Figure 5 the area of Ortenberg is split up in six parts with properties
shown in Table 1.
District Heating Network & Storage - 6 - Anders, Gerami, Hussein
Figure 5: Ortenberg split up in six areas
Considering the share of the area you can say simplified that the heat distribution
shall look the same way.
Area Color Area in m² share in % heat in kW
1 blue 194.082,32 19,63 3.573,22
2 red 175.155,65 17,72 3.224,77
3 green 156.182,58 15,80 2.875,46
4 yellow 259.488,96 26,25 4.777,42
5 purple 95.478,33 9,66 1.757,84
6 brown 108.158,46 10,94 1.991,29
total 988.546,30 100 18.200
Table 1: Properties areas Ortenberg
According to these data we planned our pipes for the net.
District Heating Network & Storage - 7 - Anders, Gerami, Hussein
4 Connection to Solar Collectors
Referring to the technical specs provided to us by Group 4 (Solar Properties), we
were able to calculate the total flow rate that should be supplied by the main feeding
hot water grid pipes to each solar thermal system mounted on each home. After
compensating for the total losses done by the pipes and fittings, the main feeding
pump should deliver a net mass flow rate value of around 450 kg/s of water as each
solar thermal system will need around 0.05 kg/s, we were able to calculate the
different values of the flow rates distributed among the different zones, we had to fix
the linear velocity of the water in the main grid pipes at 2 m/s in order to have the
different pipe sizes. As we calculated the pipe sizes, we compared it to the closest
standardized pipe sizes according to Stahlrohre DIN 2440/2448 standard.
Afterwards, the new sizes from the standards are adopted to calculate a corrected
value for the velocities with which the pumps should operate. Both the lengths and
the material of the pipes have been recognized and the costs of investment
(including: mounting, installation) and maintenance have been calculated
consequently.
Finally, the connection between the household installations and the grid pipes (the
branches) should be done in cooperation with group 4 for more accurate results.
Figure 6: District Heating Network P&ID
District Heating Network & Storage - 8 - Anders, Gerami, Hussein
Figure 6 shows the P&I-diagram of the heating grid. In frame is the part of our group,
the delivery of energy is part of the CHP group, regarding pumping the hot water
from the CHP to the thermal storage tank.
5 Thermal Storage
Thermal energy storage comprises a number of technologies that store thermal
energy in energy storage reservoirs for later use. They can be employed to balance
energy demand between day time and night time. The thermal reservoir may be
maintained at a temperature above (hotter) or below (colder) that of the ambient
environment. The applications today include the production of ice, chilled water, or
hot water which is then used to heat environments during the day.
Thermal energy is often accumulated from active solar collector or more often
combined heat and power plants, and transferred to insulated repositories for use
later in various applications, such as space heating, domestic or process water
heating. In our case according to following calculations we need a buffer tank with
capacity of 288 m3 for a 10 MWh thermal storage. That means a buffer tank with
dimensions of 9 m (length), 8 m (width) and 4 m (height) and with Storage capacity
calculations of
(1)
assuming a temperature difference of ΔTStorage = 30 K.
District Heating Network & Storage - 9 - Anders, Gerami, Hussein
Selected Storage:
Enameled Water Tank; FOB Xingang, Tianjin, China
Figure 7: Water Storage Tank
Material: Enameled steel plate.
Shipping Volume: 45 m3
Package: Wooden pallet.
Payment Term: 30% prepay by T/T, the balance 70% paid before shipment by T/T.
Delivery Time: 30 days on our receipt of your prepay.
Price Validity: 30 days.
Guarantee Period: 12 months
Item Price
storage tank 15,099.48 €
insulation 5,124.67 €
transportation 3,813.00 €
installation 1,682.60 €
total 25,719.75 €
Table 2: Tank Assorted Costs
For details see Attachment 1: Description for water storage.
District Heating Network & Storage - 10 - Anders, Gerami, Hussein
6 Pipes and branches
According to chapter 3 the overall area is divided in six areas. These six areas have
to be delivered with heat.
Figure 8: Heating grid with storage and pumps
We agreed on putting three times two pumps (Figure 8) for the grid of the district
heating and domestic hot water (for details on the pumps see chapter 7).
As shown in Figure 5 the heat that has to be transported is split up in several parts.
One pump has to deliver to area 1, another pumps has to deliver to area 2 and the
last (the biggest one) to the remaining areas.
So the heat is converted via calculation in volume flow assuming a certain
temperature difference. So for the big pipes and branches in Figure 5 the size and
length (determined via Google Earth©) can be calculated. This calculation gives the
following data.
District Heating Network & Storage - 11 - Anders, Gerami, Hussein
pipes (one line): length (m)
DN 300 1.546,32
DN 200 328,75
DN 150 1.659,12
DN 125 296,72
DN 100 253,58
Σ 4.084,50
Table 3: District Heating pipe properties
In a similar project that maybe will be realized in Oberharmersbach, the following
details are known. “Die Netzlänge ist bei angenommenen 225 Anschlussnehmern auf
10700 Metern berechnet” (Offenburger Tageblatt, [1]).
It says that the length of the grid in Oberharmersbach will reach a value of 10.700 m
taking all the small pipes into account. That is not included in the calculation for the
grid of Ortenberg.
The costs for the pipes (material & insulation) and the mounting can be seen in
chapter 8).
Added to the district heating grid the grid for the solar thermal has to be calculated
as well. Therefore some assumptions have to be made.
- distribution of solar thermal gain is the same as the demand of heat
- grid of solar thermal goes alongside with district heating grid
- taking the same pipe sizes as the district heating regarding costs and
maintenance issues
By assuming the same pipe sizes we could in case of maintenance replace one
pump from one grid to the pump from the other grid. Also the costs for the pipes are
reduced due to higher number of fewer pipes.
In this case the heat losses can be neglected due to a good insulation. Only the
pressure losses have to be compensated by pumps (see next chapter: Pumps)
There were some ideas about another type of pipe. The four-pipe-system,
where two supply and two return pipes are mounted together in one bigger
pipe is mainly installed in households for the sanitary and for the domestic
District Heating Network & Storage - 12 - Anders, Gerami, Hussein
hot water cycle. An extension to the size of the planned pipe in this report
was not found.
7 Pumps
The Grundfos HS horizontal split case pump is a single-stage, non-self-priming,
between bearing, centrifugal volute pump. The axially split design allows easy
removal of the top casing and access to the pump components (bearings, wear rings,
impeller, and shaft seal) without disturbing the motor or piping.
The independent bearing housing allows for ease of maintenance without removing
the top casing. The double volute design reduces the radial load on the shaft,
extending component life, minimizing vibration and providing quiet operation.
The HS pump also offers high pump efficiencies throughout the range. High energy
efficiency along with long pump life and easy maintenance add up to low life-cycle
costs.
The HS pump is available in three configurations – pump with motor and base
frame, pump with base frame, and bare shaft pump only.
The HS pump is ideal for custom applications and is available in a wide range of
variants. The high efficiency and low life cycle costs make the HS ideal for any
commercial building, water utility or industrial project.
7.1 Applications
Grundfos HS horizontal split case pumps are typically used in these applications:
Air-conditioning/heating systems, Public water supply, District cooling/heating plants,
Cooling systems, Public waterworks, Process cooling, Irrigation.
7.2 Features and benefits
Double suction minimizes axial load, which extends the life of the shaft seals
and bearings
Double volute reduces radial forces and minimizes noise and vibration
District Heating Network & Storage - 13 - Anders, Gerami, Hussein
Independent bearing housing design allows access to the pump components
without removing the top half of the casing
High energy efficiency
Many product variants available.
Low life-cycle costs
Easy to service: split case design
Figure 9: District Heating Pump
Branch m³/h Pump
flow rate 1 155
HS-2 pole - 125-
100-305
flow rate 2 140
HS-2 pole - 125-
100-305
flow rate 3 500
HS-4 pole - 350-
250-630
2 pumps per line
(DHN and solar thermal) Pump costs [€]
for line 1 5.000
for line 2 5.000
for line 3 15.000
total 100.000
Table 4: Pumps for main branches Table 5: Costs for pumps
District Heating Network & Storage - 14 - Anders, Gerami, Hussein
8 Equipping the Grid
Figure 10: Project PF Diagram
As the main process flow diagram has been developed for the project, we were able
to classify and quantify all the equipment used for connecting both the solar collector
network and the CHP network to the mixing storage tank.
Since the distribution from the main solar collector network and its main branches as
well as the main district heating water network and its main branches to feed from
and to each house is very hard to be anticipated, an increase in equipment quantities
and costs in these branches should be added by an amount of 30%.
Costs and properties of the insulation were given by Prof. Pfafferott in the
lecture “Planning and Operation”.
District Heating Network & Storage - 15 - Anders, Gerami, Hussein
Component Number of Units Cost (€)
Hydraulic water pumps 12 84.000
Water Storage and Mixing Tank 1 25.700
Water Filtration unit 1 20.000
Investment Costs (grid) - 3.758.000
Pipes cost (material) 4100 (m) 1.090.500
Pipe insulation costs 1665 (m3) 580.000
Mounting cost 42 €/m2 1.092.000
Connection to households - 3.452.000
pumps 12 (2 times 6) 100.000
total 10.118.200
Figure 11: Installed units and costs
Component Number of Units Cost (€)
Maintenance cost (District) 5.79 €/MWh*a 150.000
Maintenance cost (Solar) 5.79 €/MWh*a 140.000
total 290.000
Figure 12: Variable costs
9 Operation and Maintenance
Continuous fault analysis and leak detections are required to prioritize intervention,
both from design and maintenance. Furthermore a continuous monitoring of the
effectiveness and efficiency of the maintenance plan is important.
District Heating Network & Storage - 16 - Anders, Gerami, Hussein
Continuous maintenance and replacement of technical components keeps the use
of heat on the right level and improves the life length of the substation. Especially the
regulating devises such as valves and actuators have a significant impact on the life
time and must be maintained appropriately.
In order to handle dimensioning of substations in an effective way and to achieve
optimal solutions concerning the demand for heat and warm water it is essential to be
aware of the conditions and technical features of the system in use.
Control valves for both heating and domestic warm water should not be
unnecessarily large. There are a number of disadvantages with over-sized valves. By
reducing control valve sizes substantially down to the actual capacity demanded by
the customer for both heat and domestic warm water there will be a number of
benefits for the district heating network.
Regarding pipes and heat exchangers there can indeed be advantages in having
some extra capacity for the future. Also, regarding heat transfer in the heat
exchanger and the cooling of the return water larger sizes can be useful. But when it
comes to valves the situation is totally different. Here, unnecessary over-
dimensioning will result in great disadvantages for the network and production.
It is recommended that the sizing of control valves is made in accordance with the
curves shown below. This will result in a number of advantages being in line with
adequately sized heat exchangers and representing use of the smallest possible
valves.
District Heating Network & Storage - a - Anders, Gerami, Hussein
Attachment
Attachment 1: Description for water storage