Case_Study_Project_WS2012-2013_Group 1_Anders_Gerami_Ahmed_20130123

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


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.


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


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


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.


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.


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


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.

http://en.wikipedia.org/wiki/Thermal_energy

http://en.wikipedia.org/wiki/Thermal_energy

http://en.wikipedia.org/wiki/Energy_storage

http://en.wikipedia.org/wiki/Ice

http://en.wikipedia.org/wiki/Solar_thermal_collector

http://en.wikipedia.org/wiki/Thermal_insulation


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.


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.


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


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


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


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”.


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.


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

Case_Study_Project_WS2012-2013_Group 1_Anders_Gerami_Ahmed_20130123

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