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Ecofys SL

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Ronald Voskens (Ecofys, Spain)

Frank Zegers (Ecofys, The Netherlands)

June 2005

EPL04068

by order of:

Gramsbergen Solar

As part of IEA task 29 from the International Energy Agency (IEA)

SOLAR DRYING IN EUROPE

Solar Drying in Europe, Ecofys, 2005 II

SUMMARY

To finalize the IEA task 29 Solar Crop drying, Ecofys was contracted by Grams-

bergen Solar to contribute to finalising the Dutch work in this task by answering the

following questions:

• What is the current status of solar drying in Europe?

• Compile a basic calculation tool for solar dryers in Europe?

The limited span of the contract did not enable to give an extensive update of the

current status of solar drying in Europe. However the information found will give

an adequate impression of the state of the art of the solar drying market in Europe.

The update shows that a significant number of solar drying plants have been built

throughout Europe (some 4000) with a total solar drying collector surface area of

more than 1,2 million m2. The majority of the plants (and 80% of the collector sur-

face) have been built in Switzerland for forage drying. Furthermore sewage drying

on a large scale has come up recently quite strong (110,000 m2).

Although solar drying systems in general are self made system or integrated in the

building process of new build barns there are some manufactures/suppliers active

throughout Europe. SolarWall sells perforated air collectors, Grammar Solar glazed

and unglazed air collectors, ICT Anlagebau and Thermo-system greenhouse solar

dryers and Innotech solar tunnel dryers. Mostly these suppliers are selling their sys-

tem in a broader sense. As well in products to be dried (like sewage) as well in ap-

plication non-drying (pre-heating of ventilation air).

Monitoring projects show that solar contributions of 50-100% are feasible depend-

ing on product and type of solar drying system.

A simple spreadsheet tool has been made to estimate the optimum size and the eco-

nomic feasibility for a solar air collector drying systems. The tool is based on

monthly values and is meant for a first indicative feasibility analysis.

Some guidelines have been compiled in order to stimulate an integral design ap-

proach for the planning of solar drying systems. A short description of the so-called

‘trias energetica’ approach has been introduced for this purpose:

1. Reduce the energy demand

2. Use sustainable energy

3. Use fossil energy in the most efficient way

Solar Drying in Europe, Ecofys, 2005 III

Table of contents

1 Introduct ion 1

1.1 Introduction 1

1.2 IEA task 29 Solar crop drying 1

1.3 Potential for Solar drying 2

1.4 Classification of solar dryers 3

1.5 Classification of collectors 4

2 State of the art , Solar Drying in Europe 7

2.1 Introduction 7

2.2 Overview 7

2.3 The manufactures side 10

2.4 Monitoring results 14

3 Simple tool , Rules-of-the-thumb 18

3.1 Energy demand 18

3.2 Contribution of solar energy 20

3.3 Economic analysis 23

4 Integral approach 27

5 Conclusions 28

Solar Drying in Europe, Ecofys, 2005 1

1 Introduction

1.1 Introduct ion

To finalize the IEA task 29 Solar Crop drying, Ecofys was contracted by Gramsbergen

Solar to contribute to finalising the Dutch work in this task by answering the following

questions:

• What is the current status of solar drying in Europe?

• Compile a basic calculation tool for solar dryers in Europe?

The limited span of the contract did not enable to give an extensive update of the current

status of solar drying in Europe. However the information found will gave an adequate

impression of the state of the art of the solar drying market in Europe.

1.2 IEA task 29 So lar crop drying

1.2.1 Introduct ion IEA task 29

One of the most promising applications for active solar heating worldwide is the drying

of agricultural products. In a 1999 study produced by Enermodal (Canada) and Ecofys

(the Netherlands) [1], the potential amount of energy that could be displaced using solar

in this market was estimated to be between 657PJ and 1530 PJ annually. The most prom-

ising market for solar drying in general are those crops that are mechanically dried at

lower temperatures.

Crops that are currently sun-dried are well suited to solar drying, but the financial re-

sources to implement a solar drying system are often lacking. The processes that are used

to dry crops at temperatures greater than 50ºC could benefit from solar drying as a sup-

plemental system, but the drying process must be re-organized. Therefore, this Task will

concentrate on displacing fuel-fired dryers for crops that are dried at temperatures less

than 50 degrees Celcius.

The identified potential for displacing conventional energy sources in this segment of the

market is estimated to be between 300 PJ and 900 PJ. The use of solar energy for these

markets is largely undeveloped. Other than open air drying, wood and conventional fossil

fuels are used most extensively at present. In many countries more expensive fuels like

diesel and propane are replacing wood.


Three key barriers to increased use of solar crop drying identified by the above study are

the lack of awareness, the lack of good technical information and the lack of good local

practical experience.

1.2.2 Objec t i ves IEA task 29

The objective of this Task is to address the three barriers above by providing technical

and commercial information and experience gained from the design, construction and op-

eration of full working demonstration systems for a variety of crops and a number of

geographical regions.

1.3 Potent ial for Solar dry ing

In 1998/1999 a study [1] was commissioned to better understand the technical and eco-

nomic potential for solar drying of agricultural products in the world. This was a joint

project of Canada and the Netherlands under the direction of the IEA Solar Heating and

Cooling Program. The objectives of this project included: estimating the potential world

market for solar drying of agricultural products, and identifying promising agricultural

products and geographic regions for solar drying. For each of the 59 crops and 22 regions

the practical potential for solar drying was determined. The world market for solar drying

can be divided into three market segments, as indicated in the table below:

Table 1.1: Market Segments

Market

Segment

Current drying

method

Level Desirable future dry-

ing method

1 Mechanical drying

T< 50°C

Farm, Village,

Factory

Partly replaced by

solar drying

2 Mechanical drying

T>50°C

Factory Add solar drying

3 Sun drying Farm Replaced by solar

drying

The world market for solar drying of agricultural products ranges between 677 PJ and

1530 PJ annually, as shown in the table below.

Table 1.2: Energy Displaced by Solar

Potential Amount of Energy Displaced by

Solar (PJ)

Low High

1) dried at T < 50°C 216 770

2) dried at T > 50°C 41 111

3) sun dried 420 649

Total 677 1530


For the most promising market segment (mechanical drying, T< 50°C) the potential

ranges between 216 and 770 PJ. In financial terms this is the equivalent of 17 to 60 bil-

lion € (investments in solar dryers). In collector area this is the equivalent of 0.3 – 1,2 bil-

lion m2. On the basis of the results of this study rough estimations were made on total

collector area, labour, CO2 reduction and turnover. The results for the market segment

mechanically dried at lower temperatures are summarised is the next table. A breakdown

was made for Western and Eastern Europe, see also appendix A for an overview of

Europe.

Table 1.3: Pract ical potent ia l for solar drying

Potential World Western

Europe

Eastern

Europe

low high low High low high

Practical potential [PJ] 216 770 23 88 7 13

Collector area [m2

*106]

340 1200 35 140 10 20

Labour [103 man-year] 85 300 9 35 3 5

ton CO2 106 12.3 43.9 1.3 5.0 0.4 0.7

Turnover [109

€] 17 61 1.8 7 0.55 1

1.4 Class i f i cat ion o f so lar dryers

There is a wide range of active solar dryers in use around the world. They can be divided

in four main types of solar dryers: natural convection, forced convection, both direct and

indirect (see next table). For Europe the focus is on forced convection solar dryers be-

cause of the need to be compatible with fossil-fuel dryers, which are normally use forced

convection. Furthermore, indirect systems can be easily retrofit to fossil-fuel drying sys-

tems.

Table 1.4: C lass i f icat ion of solar dryers

Natural convection Forced convection

Direct Indirect Direct Indirect

Open air dryers e.g. Tent dryer e.g. Cabinet

dryer

e.g. Solar tunnel

dryer

e.g. Cabinet

dryer with venti-

lator

Structure inte-

grated dryers

e.g. Greenhouse

dryer

e.g. Barn with

natural convec-

tion

e.g. Greenhouse with ventilator

e.g. Barn with

integrated col-

lector and venti-

lator


1.5 Class i f i cat ion o f co l l ectors

In general all solar dryer collectors can be classified in three main types of solar dryer

collectors: unglazed collector, glazed collector and the perforated plate collector. The

collector efficiency and estimated investment costs are summarised in the next table.

Table 1.5: e f f ic iency and investment costs of ai r col lectors

Type of collector Unglazed Glazed Perforated

Efficiency (%) 30-40 40-50 60-70

Investment costs (€/m2) 25-30 40-50 100-150

1.5.1 Unglazed Co l lector

An unglazed (or back pass) collector consists of a dark coloured metal plate with a cavity

below (see figure 1.1). This dark surface, or absorber, absorbs direct and diffuse solar ra-

diation and transfers this heat to the air flowing below the absorber. The (existing) roof-

ing (e.g. corrugated sheet metal) of a building can be painted a dark colour and serve as

the absorber. A cavity is created between the absorber (the roof) and a (insulated) back

plate. Suitable back plate materials would be wooden panels or insulating board. The

construction should be reasonably airtight to prevent air leakage from the outside. Alter-

natively a dark metal sheet can be mounted on top of the roof as the absorber. In this case

the space between the roof and the metal plate serves as the airflow channel. The effi-

ciency of these collectors compared with other collector types is fairly low (i.e. 30-40%).

The low efficiency is due to high to heat loss to the ambient: convective losses to the

wind and radiative losses to the sky.

Figure 1 .1: Unglazed Solar Col lector

Solar

radiation

Cavity

Absorber

Insulation

Air flow


1.5.2 Glazed Col lector

Glazed collectors consist of a black surface, such as metal, plastic, painted wood, as the

absorber and a cover of glass or transparent plastic sheets (see figure 1.2). The transpar-

ent cover reduces long-wave radiation from the absorber to the sky (so called greenhouse

effect). The air can be blown either between the absorber and transparent cover or be-

tween the absorber and a back plate or both. If the air is blown below the absorber, the

stagnant air between the absorber and cover helps to reduce heat loss to the wind. An-

other option is to make the absorber out of a fibrous material (sometimes referred to as

fibre matrix collector). The air enters between the glazing and absorber, flows through

the fibre matrix absorber and exits between the absorber and insulation. Glazed collectors

have higher efficiencies (i.e. 40-50%) than unglazed collectors, albeit at higher cost.

Figure 1 .2: G lazed Solar Col lector

1.5.3 Per forated Plate Co l lector

The perforated plate (or transpired) collector is similar to an unglazed solar collector ex-

cept that the solar absorber has many small holes or perforations in it (a porosity of about

1%). Instead of the air passing along the absorber like in the other collector types, the

outside air is sucked through the perforated absorber (see figure 1.3). The absorber heat is

then transferred to the incoming air. By pulling air through the absorber, heat loss to the

wind is greatly reduced. These perforated collectors can reach a high overall efficiency,

i.e. 60-70%.

Solarradiation

Transparentcover

Cavity

Absorber

Insulation

Air flow


Figure 1 .3: Per forated Plate Solar Col lector

Solarradiation

Cavity

Absorber

Insulation

Air flow


2 State of the art, Solar Drying in Europe

2.1 Introduct ion

The information used in this chapter is based upon the report Solar drying of Agriculture

produce in Europe [2] and updated with information from contacted experts and organi-

sations in Europe. See for an overview of contacted experts and organisations appendix

B. By its nature solar drying systems are mostly self-build systems or directly integrated

in the construction of the barns. Therefore it is not easy to find good statistics on realized

systems. Another fact that has to be taken into account is that solar drying in general is

not on the political agenda, which also make is hard to find reliable country information.

2.2 Overview

Solar drying of agriculture produce in Europe,

1992

Updated 2005 (additional information)

Country # systems

m2

Type of prod-

uct

# systems

m2

Type of product

4 Forage

Medical plants

Fruits

Vegetables

1

1

Seeds

Sewage (200 m2, green-

house)

Belgium

0 m2 4700 m

2

100

5

12

Forage

Cereals

Medical plants

150 - 200

36

?

Forage

Sewage (48632 m2, green

house)

Tunnel dryer

France

37700 m2 68632 m

2

Norway 150

100

Cereals

Forage

n.d.

> 300 Cereals

Forage

Wood

Beans

n.d. Sweden

90000 m2

7

16

1

2

Cereals

Forage

Tobacco

Vegetables

1 Sewage Poland

4700 m2



1992


Country # systems

m2

Type of prod-

uct

# systems

m2

Type of product

Former

Czechoslovakia

150 - 200 Forage n.d.

> 100 Forage

Fruit

Vegetables

Seed

1

?

Sewage

Tunnel dryer

Hungary

3000 m2

Romania 60 Cereals

Tobacco

Fruits

Vegetables

Wood

n.d.

Greece 1 Fruit n.d.

Former Yugo-

slavia

? Fruits

Vegetables

Tobacco

Mushrooms

n.d.

20 - 30 Forage

Cereals

Tobacco

Wood

Medical plants

Fruits

Vegetables

2

1

?

Noodles


house)

Tunnel dryer

Italy

15000 m2 320 m

2

200 Forage

Cereals

Seed

Medical plants

Vegetables

31

2

?


house)

Wood (300 m2, green house)

Tunnel dryer

Germany

50000 m2 33040 m

2

1250 Forage

Cereals

Fruits

1019

3

Forage


house)

Switzerland

460000 m2 374580 m

2

30 - 40 Cereals

Fruits

? Tunnel dryer Portugal

5000 m2



1992


Country # systems

m2

Type of prod-

uct

# systems

m2

Type of product

2 Fruits 1

?

Ham

Tunnel dryer

Spain

300 m2 80 m

2

2

40

Forage

Cereals, wood

n.d. United King-

dom

6600 m2

7

10

Unions

Flower bulbs

Cereals

Flower bulbs pre-heated air

by green house

The Nether-

lands

2200 m2

Finland 70000 m2 (2002)

10

1

Sewage (11987 m2)

Wood (100 m2)

Austria

12087 m2

TOTAL ~2587 ~1374 total: ~3961 systems

~665,000 m2 ~575,000 m

2 total: ~1,240,000 m

2

n.d. = no new additional data found

One can conclude that a significant number of solar drying plant have been built through-

out Europe (some 4000) with a total solar drying collector surface area of more than 1,2

million m2. The majority of the plants (and 80% of the collector surface) have been built

in Switzerland for forage drying. Furthermore sewage drying on a large scale has come

up recently quite strong (110,000 m2)

The Netherlands

From the demonstration plants realized in the Netherlands it was clear that solar drying of

flower bulbs (in general) with solar energy is feasible. Till today about 7 systems are re-

alized. However the market penetration is still quit low. The main reasons for that are:

• No targeted marketing campaigns were carried out

• The flower bulb breeders are not really interested due to low costs of drying energy

in relation to the total costs and the risk of intervention in the normal drying process

that could harp their market product (flower bulbs)

Last years the DLV (Dienst Landbouw Voorlichting – Information Centre of the Ministry

of Agriculture) did some work on the field of using pre-heated air from greenhouses

(normally available in combined flower bulb breeding farms). Up to no around 10 sys-

tems are in operation.


Switzerland

Hay drying is needed to produce some typical types of cheese (Hartkäse, wie Emmen-

thaler, Greyerzer etc.). This is one of the secrets of Swiss cheese. One cannot use semi

dry conserved grass (and others products) in wintertime (Silofutter: This in plastic con-

served hay you see today everywhere). To have really dry hay it helps to finalise the dry-

ing in the stock. To reduce energy consumption it helps to preheat incoming air e.g. by

solar energy. Some years ago, all cheeses were produced with dried hay only. Nowadays,

only the mentioned types still are using this method.

Another item to take into account is the structure of agriculture. More and more, even in

the mountains, the mechanisation on harvesting hay was improved a lot, so one can dry

the hay in the outside air until the last minute (before the evening or an upcoming thun-

derstorm, which appears to be very often in the mountains). Before the hay was gathered

often a little bit too early, which gave unwanted chemical reactions in the stock.

In 1980 special campaigns for the agricultural sector were carried out. Since more than

15 years no additional campaigns took place.

So the number of newly installed hay dryers goes down and an increasing number of

older ones are not in use anymore.

Belgium

The owner and user of the solar drying plant Dumon Agro reported that he was very sat-

isfied with solar drying systems and that it met the expected results.

2.3 The manufactures s ide

Although solar drying systems are in general self made system or integrated in the build-

ing process of new build barns there are some manufactures/suppliers of solar drying sys-

tems or collectors in Europe selling their equipment. From the main suppliers a small

summery is given in the paragraphs below. One remark is that these suppliers are selling

their system in a broader sense. As well in products to be dried (like sewage) as well in

application non-drying (pre-heating of ventilation air).


2.3.1 SolarWal l

SolarWall is the Canadian manu-

facturer of perforated collector

plates for air collectors (for solar

drying as well as for pre-heating

ventilation air). SolarWall has

also a branch office in Europe,

Germany. SolarWall real-

ized/sold 2 solar drying systems

in Europe to date. 100 m2 for a

wood drying plant in Austria and

80 m2 for ham drying in Spain.

Wood drying with SOLARWALL

Biowärme Klein St.Paul (Kärnten, Austria) is a central district

heat power plant company. They supply district heat to a large

part of the households in that area. They are firing shreddered

wood and bark, which are delivered by local farmers often wet

and green. They must be dried before they can be burned. This

is an ideal application for a solar air collector like SOLARWALL.

Preheating air is drawn through a 45° sloped, roof mounted and

south oriented SOLARWALL air collector field. In the summer

time temperatures of > 70° C have been produced by solar ra-

diation only. The temperatures have been risen by solar power

for more than 30° C over ambient.

The southbound collector field is 19,2 m wide and 5,30 m high,

thus measuring totally 100 m². A standard steel profiled sheet

was used for the undercover in order to get rid of the water. A

metal construction allows an air gap. The SOLARWALL sheets

are mounted on top of this metal construction. Through metal

tubes the air is taken inside the building. The fan has a capacity

for 7200 m³/h

Air channels cover the floor of the drying building, which is cov-

ered by perforated sheet. The shredded wood is driven on

those sheet. The solar preheated air is now blown from the roof

underneath the drying bed through air channels. The wood is

ventilated and dried.


2.3.2 Grammer So lar

Grammer Solar is a German manufac-

turer of glazed and unglazed air collec-

tors. The collectors have a typical size

of several square meters and can be

combined in parallel or serial to get a

bigger collector area. Grammer real-

ised a couple (ca. 6) of solar drying

systems mainly in Germany with a to-

tal collector area of about 400 m2 with

air collector. Besides this system

Grammer reported that they also put a

greenhouse solar drying plant into op-

eration in 2002 with a collector area of

860 m2.

2.3.3 ICT Anlagebau and Thermo-System

These 2 suppliers are the main suppli-

ers for greenhouse solar dryers in

Europe. The main product for drying is

sewage sludge and in some cases

wood. All together they claimed a total

number of 85 systems installed

throughout Europe with a total collec-

tor area of about 110.000 m2. The main

market at the moment is France

(48.000 m2) and Germany (33.000 m

2).

With well-stabilized sludge having an

organic matter below 60% there are no

problems. Sludge which is unstable e.g.

organic matter above 70%, risk the de-

velopment of bad odours due to the

fact that the mechanical dehydration is

less good (below 20% dry solid DS)

and when turning during the drying

process, they have the tendency to be-

come a paste and then anaerobic. One

can avoid that by regularly turning the

sludge e.g every day 4 to 6 times.

Picture 2.3: Glazed col l ectors of

Grammar Solar

Figure 2 .4: Sewage drying plant from

ICT Anlagebau in Poland.

4.700 m 2

Figure 2 .4: Sewage drying plant from

Thermo-System in Aust ia.

3.250 m 2


Up to DS about 60% the thermal dehydration is relatively constant, above that it takes

much more energy and the drying process slows down. The natural end stadium in a solar

thermal dryer is around 90% of DS and the product is very stable when stored, as it has

then no moist kernels, which is the risk with industrial dried sludge. The annual evapora-

tion is highly depending on the annual incident solar radiation, varying around 800

kg/m²year in middle Europe.

The cost of final treatment of sludge is transferred to the households include in the prize

of fresh water. There is little pressure to lower the cost and the water works search more

for safe solutions in form of long-term contracts than saving cost.

Solar dried sludge requires very little auxiliary energy only 10 to 30 kwh/t of water

evaporated. Industrial dried sludge requires 800 to 1000 kWh. Therefore solar dried

sludge is a renewable source of biomass, which can be incinerated like wood. The differ-

ence is only that it grows in basins and not in the forest.

2.3.4 Innotech

The solar tunnel dryer type "Hohenheim"

unites simple construction, use of renew-

able energy and easy handling. This

dryer is particularly applicable for pro-

duction of high quality products in agri-

cultural enterprises. As a cooperative de-

velopment of the Institute for Agricul-

tural Engineering in the Tropics and Sub-

tropics of Hohenheim University and

INNOTECH Engineering Ltd., solar tun-

nel dryers are in commercial operation in

more than 60 countries all over the

world.

In Europe the solar tunnel dryers are realized in the next countries: Austria, Cyprus,

France, Germany, Greece, Hungary, Italy, Portugal, Romania, Spain, In total Innotech

claimed to have around 50 solar tunnel dryers in operation throughout Europe. The dryers

are used to dry: apples, mushrooms, herbs, orange peels, apricots, grapes, plums and to-

matoes.

The solar Tunnel dryer in its standard version is applicable for drying of nearly all agri-

cultural produce under various climatically conditions.

Technical data:

• Length 18 m

• Width 2 m

Figure 2.5: Solar tunnal dryer type

“Hohenheim”


• Collector area 16 m²

• Drying area 20 m²

• Air flow rate 400 -1 200 m³/h

• Air temperature 30 - 80 °C

• Power requirement 20 - 40 W

• Drive of fans Solar panel

• Thermal energy gain from solar radiation from 60 kWh/day

Set up 1 day

2.4 Monitor ing resul ts

In the paragraph some results are presented of monitoring project carried out in Europe.

2.4.1 The Noord , the Nether lands

In 1996 a first demonstration project in the most promising sector (flower bulbs) in the

Netherlands (“De Noord I”) was set up. Within this demonstration project a monitoring

system was installed to evaluate the performance of the system (2 seasons). In 1999 a

second demonstration projects (“De Noord II”) was set up with a new build collector.

Results De Noord I

The performance of the system (200 m2 unglazed collector area) has been monitored dur-

ing two drying seasons (95/96 and 96/97). The result of the second drying season is

summarised in the flowchart below [5].

Conclusions:

• The system operates without any problem.

• The solar systems covered up to 40% of the energy demand for drying.

• There is a strong correlation between the efficiency of the collector and air flow

through the collector. By increasing the airflow from 30 to 70 m3/m2.hour the effi-

ciency of the collector increases from 25 to 37%.

• The monitoring programme showed that in the present arrangement there is still room

for improvement of the exciting installation’s performance.


Solar irradiation415 GJ

Used primaryenergy501 GJ

Utilised solarenergy152 GJ

Used energyfor drying398 GJ

Spaceheating52 GJ

Not utilisedsolar energyand collectorlosses262 GJ

Losses(boiler anddistributionpipes)216 GJ

Utilised energy233 GJ

Results De Noord II

The performance of the system

(180 m2 unglazed collector area)

has been monitored during two

drying seasons (1999 and 2000).

The most important results are

summarised below [6].

• The system operates without

any problem.

• During this monitoring pro-

ject the airflow through the

collector was 30 m3/m

2. The

overall efficiency of the col-

lector was 28%.

• The solar systems covered up to 50% of the energy demand for the specific heat

treatment.

• The used frequency regulator for the circulation fans (optimise demand and supply)

gives a saving of 80% on electricity consumption.

2.4.2 Dumon Agro , Be lg ium

Based upon the experiences and results of the demonstration project de Noord I with a

simple solar drying system in the Netherlands for flower bulbs, a Flemish handling and

trading company in seeds (Dumon Agro/Daso nv) constructed a solar collector is their

new build transit store house. The system came into operation in 1998. The system has a

Figure 2.1: A ir co l lector under

construct ion (De Noord II)


total solar collector area of circa

4.500 m2 (unglazed). The company

has a total storage capacity of circa

4.000 m3 seeds. For drying only a

maximum of 2.000 m3 seeds is being

dried at the same time. The applied

ventilation rate was about 60 m3/m3

product.

During the drying season of 2000,

VITO carried out a detailed monitor-

ing project of this system. [3]. The

main results of this drying season can

be summarized as follows:

• Total energy produced by so-

lar 323,3 GJ.

• Average temperature rice of

the collector was 6,5ºC

(maximum 19,3ºC)

• Total solar contribution to

the drying system was 49%

• Overall collector efficiency

was 6,2%

• CO2 reduction 20,4 ton/year

Note 1: Due to an agricultural crisis

in this year the installation only was

used at 1/3 of the maximum capacity.

Note 2: The total monitored collector

efficiency over the drying season is

quite low. The reason for that can be

found in the quite low airflow in the

collector in the range of 5 – 15

m3/m

2.h.

Figure 2 .2: Solar drying plant Dumon Agro

(4,500 m 2)

0

50

100

150

200

250

300

350

400

450

Ju

ly

Au

gu

st

Se

pte

mb

er

Octo

be

r

month

GJ/m

on

th

Fuel

Solar

Figure 2 .3: Moni tor ing resu l ts solar drying

plant Dumon Agro (2000)


2.4.3 Wolf rathausen, Germany

In 1997 a solar drying system with

Grammar glazed air collectors (74 m2)

was realised for drying of different types

of bio fuels (like: wood chips, forest

chips, billet wood, sawdust, bark etc.

This system works without a back-up

heater so 100% solar contribution was

realized, [4].

Goal of the planning and construction of

the solar drying plant was an energeti-

cally optimised drying procedure with

minimal initial costs and low operating costs. Therefore the drying equipment was de-

signed to minimise the power requirement by the fan. This was accomplished by care-

fully constructing of the drying facility enabling to reduce pressure drop in the air canals

and by using minimal air flow rates.

The specific airflow rate through the collectors can be adjusted from 40 to 100 m³/m²/h

(from 3,000 to 7,500 m³/h). This corresponds with a collector efficiency of up to 68 %.

At a solar radiation of 1.000 W/m² the thermal peak output then is 51 kW. The annual

output of solar heat amounts to 53.0 MWh and the annual throughput of wood chips

amounts to 1,050 m³/h, see also next table.

Parameter Result

output of solar heat: 53.0 MWh/a

maximum temperature rise: 45.0 K

annual throughput of wood chips (wet material): 1,050.0 m³/a

water-evaporation: 51.0 t/a

duration for drying one pile (average value): 24.0 days/pile

annual current consumption: 2.6 MWh/a

total power requirement (average value): 0.8 kW

avoidance of dry matter losses: 31.1 t/a

absolute increase in the calorific value 272.0 MWh/a

expected time for amortization: 5.5 years

Table 2.1: Resu lts of the operat ion o f the solar drying plant for one year [4]

Pic ture 2.4: Solar dry ing plant


3 Simple tool, Rules-of-the-thumb

This chapter describes a method used in a spreadsheet tool to estimate the optimum size

and the economic feasibility for a solar drying system with an air collector for a given

case. This tool is based on monthly values and works fine for a first indicative analysis.

The most important input for the method is the monthly energy demand for the drying

process. It is also possible (in the case a drying system is already in use) to estimate the

demand on monthly energy use (fuel). The second step is to estimate the possible contri-

bution of the solar energy to the drying process, in relation to: 1) climate conditions, 2)

collector type and 3) collector area. The third step is to analyse and optimise the solar

drying system economically, based upon additional investment costs and local energy

prices.

The tool is explained for an actual case. A Dutch flower bulb farm with 4 ha of tulips and

4 ha of hyacinth. The heat demand on the farm is used for drying and conditioning of the

bulbs. The drying barn has an effective south facing roof area of 450 m2 and is equipped

with 4 drying cells. Heat is supplied by 2 natural gas fired boilers of 190 kW each.

Within the example the optimum collector area and the economic feasibility for an un-

covered solar collector with an efficiency of 35% is calculated.

3.1 Energy demand

See spreadsheet tool steps 1 and 2.

The energy demand depends on the following data:

• Ambient temperature [Ta] (choose location, spreadsheet - step 1)

• Needed temperature for the drying process [Td]

• Ventilation rate for the drying process [VR, m3/hour]

• Number of days of drying [-]

• Efficiency of the normal fossil drying equipment [Eh, %]

• Heat losses in circulations pipes for the normal drying equipment [El, %]

To calculate the energy demand (E) next formula can be used:

• E = (DT × VR × d) x (1 + El) /(Eh x 32,3) [MJ/month]

For the calculations the next table can be used (spreadsheet - step 2):


Step 2: Energy demand for drying processPlease fill out white fields Efficiency heater [%] 90% Eh

Heat losses [%] 10% El

Total

days per

month

Ambient air

temperature

Needed

air

temperatu

re for

drying

Temperature

difference

Ventilation

rate per

hour

Number of

days for

drying per

month

Primary energy

demand

(fuel)

Td Ta [°C] Td [°C] DT = Ta - Td VR d E = (DT × VR

× d) x (1 + El)

/(Eh x 32,3)

[-] [°C] [°C] [ºC] [m3/hour] [-] [MJ]

Jan 31 2.2 0.0 0

Feb 28 2.5 0.0 0

Mar 31 5.0 0.0 0

Apr 30 8.0 0.0 0

May 31 12.3 0.0 0

Jun 30 15.2 30 14.8 5100 18 51411

Jul 31 16.8 29 12.2 14200 31 203217

Aug 31 16.7 29 12.3 14000 31 201997

Sep 30 14.0 24 10.0 15000 30 170280

Okt 31 10.5 21 10.5 7550 31 92993

Nov 30 5.9 15 9.1 3000 30 30991

Dec 31 3.2 12 8.8 3000 10 9990

Total

energy

demand

760879

Month

0

50000

100000

150000

200000

250000

Ja

n

Fe

b

Ma

r

Ap

r

Ma

y

Ju

n

Ju

l

Au

g

Se

p

Okt

No

v

De

c

Month

En

erg

y d

em

an

d [

MJ/m

on

th]


3.2 Contr ibut ion of so lar energy

See spreadsheet tool steps 1, 3, 4 and 5.

The contribution of solar energy depends on the following data:

• Solar irradiation (G, MJ/m2/month)

(see spreadsheet - step 1 and sheet Add weather data)

• Energy demand profile (see spreadsheet - step 2)

• Collector area (A, m2)

• Inclinations of the collector (i) (see spreadsheet - step 3)

• Orientation of the collector (o) (see spreadsheet - step 4)

• Type of collector (collector efficiency: Ce) (see spreadsheet - step 5)

To calculate the solar energy contribution per month the next formula can be used:

• If (E/2 < Smax) then Es = E/2

• If (E/2 > Smax) then Es = Smax

Where:

• Smax = G x A x i x o x Ce = max solar heat output = max saving

• E/2 = total energy demand divided by 2, as an estimate of the energy demand

during daytime

• Es = solar energy contribution or the savings on the energy demand

The solar energy contribution (Es) is equal to the energy demand during daytime (E/2), if

this energy demand is less than the maximum solar system output (Smax). If the energy

demand during daytime (E/2) is higher than the maximum solar system output (Smax),

the solar energy contribution (Es) is limited to the solar system output (Smax).

Incl inat ion factor ( i ) per month for a locat ion wi th lat i tude 40º

INCLI. JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

0 1,00 1,00 1,00 1,00 1,00 1,00 1,00 1,00 1,00 1,00 1,00 1,00

10 1,14 1,11 1,08 1,05 1,03 1,02 1,03 1,06 1,10 1,14 1,17 1,16

20 1,25 1,20 1,14 1,08 1,03 1,02 1,03 1,09 1,17 1,26 1,32 1,30

30 1,34 1,26 1,17 1,07 1,01 0,98 1,01 1,09 1,20 1,34 1,43 1,41

40 1,39 1,29 1,16 1,04 0,95 0,92 0,95 1,05 1,21 1,39 1,50 1,48

50 1,41 1,28 1,13 0,98 0,87 0,83 0,87 0,99 1,18 1,39 1,54 1,52

60 1,39 1,24 1,07 0,89 0,77 0,72 0,77 0,90 1,12 1,36 1,53 1,51

70 1,34 1,17 0,98 0,78 0,64 0,59 0,64 0,79 1,02 1,30 1,49 1,47

80 1,25 1,08 0,86 0,65 0,50 0,45 0,50 0,66 0,90 1,20 1,41 1,40

90 1,14 0,95 0,73 0,50 0,35 0,29 0,34 0,50 0,76 1,07 1,29 1,29


Or ientat ion factor (o) for a locat ion with lat i tude 40º

Orientation (0 = south)

Factor o

0 1,00

10 0,99

20 0,98

30 0,97

40 0,94

50 0,91

60 0,87

70 0,83

80 0,77

90 0,71

Collector efficiency (Ce)

The collector efficiency depends on the air speed trough the collector. For a good effi-

ciency (heat exchange between collector plate and air) a so-called turbulent airflow is re-

quired. In principle: the higher the air speed the higher the collector efficiency. However

the higher the air speed through the collector, the higher the collector resistance and the

higher the energy consumption of the ventilator, which means lower overall energy sav-

ings. A good balance was found in an airflow rate of around 200 m3 per m2 collector per

hour (air speed of circa 4 m/s). In this case a collector efficiency of around 40% can be

obtained for an unglazed collector with a low increase of collector resistance.

For the calculations of solar contribution the next table can be used (spreadsheet - step 7):

SOLAR DRYING IN EUROPE, ECOFYS, 2005 22

Step 7: AnalysesFill out minimal and maximal collector area, capital interst rate and depreciation time

Minimal collector area 100 m2

Maximal collector area 800 m2

Capital interest rate 5% %

Depreciation term 20 years Yearly capital cost, annuity on investment: 8%

Energy

demand

m2

max real max real max real max real max real max real max real max

[MJ/month]

Jan 0 32 3189 0 5049 0 6909 0 8769 0 10629 0 12489 0 14349 0 16210

Feb 0 64 6413 0 10153 0 13894 0 17635 0 21375 0 25116 0 28857 0 32597

Mar 0 100 10002 0 15837 0 21671 0 27506 0 33341 0 39175 0 45010 0 50844

Apr 0 156 15563 0 24642 0 33720 0 42799 0 51877 0 60956 0 70034 0 79112

May 0 198 19795 0 31342 0 42890 0 54437 0 65984 0 77531 0 89078 0 100626

Jun 51411 189 18937 18937 29984 25705 41031 25705 52077 25705 63124 25705 74171 25705 85218 25705 96264

Jul 203217 205 20528 20528 32502 32502 44477 44477 56452 56452 68426 68426 80401 80401 92375 92375 104350

Aug 201997 184 18436 18436 29191 29191 39945 39945 50700 50700 61454 61454 72209 72209 82963 82963 93718

Sep 170280 130 12994 12994 20574 20574 28154 28154 35734 35734 43314 43314 50894 50894 58474 58474 66054

Oct 92993 89 8857 8857 14024 14024 19191 19191 24358 24358 29525 29525 34692 34692 39858 39858 45025

Nov 30991 47 4689 4689 7425 7425 10160 10160 12895 12895 15631 15495 18366 15495 21102 15495 23837

Dec 9990 28 2806 2806 4442 4442 6079 4995 7715 4995 9352 4995 10988 4995 12625 4995 14261

392 450

[MJ]

275 333

Month

100 158 217 508


3.3 Economic analys is

For the economic analyses the next data are important (see spreadsheet - step 6 and 7):

• Additional investments costs for the solar system

• Energy price for fossil fuel (depends on the type of fuel and the local circumstances)

• Interest rate for capital investment

• Depreciation time (time of the capital loan).

Additional investment costs

The additional investments costs can be divided into 3 main parts:

1. Additional cost for the construction of the collector, meaning additional material

costs and/or additional labour costs. In the case of integration in a new build barn the

additional material cost for the collector can be zero (in the case of a unglazed collec-

tor). Only additional labour costs have to taken into account for creating the cavity.

2. Additional costs for air ducts. The diameter of air ducts is about 1% of the collector

area (max air speed 6 m/s). The length of air ducts will be very dependent on the lo-

cal situation. In some cases there is no need for air ducts. The costs for air ducts are

significant. In this model we use the next formulas as an estimate:

a. No ducts: L = 0 (f = 0)

b. Short ducts L = 5 + 0,250,5√A (f = 0,5)

c. Normal duct L = 10 + 0,5√A (f = 1)

d. Long duct L = 20 + √A (f = 2)

Multiplying the perimeter and the length of the air duct with the costs per m2 air duct

gives the additional costs.

3. Additional costs for control and by-pass valves. These are normally fixed costs.

Based upon these 3 parts the additional investment (AI) can be calculated according the

next formula:

• AI = X + Y x √A + Z x A

X = fixed costs (control, pay-passes)

Y = f x 3,5 x cost/m2 (air ducts)

Z = f x 0,175 x cost/m2 (air ducts) + cost/m

2 (collector area)

A = collector area

Defau lt values for economic analys is

Item default own value result

Collector material 5 €/m2 5 €/m2

Labour cost 30 €/hour 4,8 €/m2

Total 9,8 €/m2

Fixed costs 2000 € 2000 €

Length air duct (f) 1

Costs per m2 70 €/m2 70 €/m2


Based upon the default values, the values for X, Y, Z are:

X = 2000

Y = 245

Z = 24

The next figure shows the costs curves for the different duct lengths (rest of the values

are default).

The exploitation costs are defined with the assumption of a lifetime of the drying system

of 20 years with a net interest rate of 5% (interest – inflation). On the basis of this the an-

nual exploitation cost are about 8% of the additional investment costs.

Exploitation benefits are defined as total energy saving multiplied by the energy price

minus the exploitation costs.

Equivalent energy price, saved energy is defined as total saved energy divided by the

exploitation costs. In other words the production costs per unit of solar energy produced.

Can be compared with fossil fuel costs.

Simple pay out time is defined as additional investment costs divided by total saved en-

ergy multiplied by energy costs.

The selection of the system size with the best economic performance can be done based

on the next table (spreadsheet step 7):

0

20

40

60

80

100

120

0 500 1000 1500 2000

Collector area [m2]

Ad

ditio

na

l in

ve

stm

en

t co

sts

[€

/m2

]

f = 0

f = 0,5

f = 1

f = 2

Costs curves for di f ferent ai r duct lengths


The system with the best economic performance has a size of 450 m2 and this area just matches the maximum roof area available.

Results

1 2 3 4 5 6 7 8 9 10 11 12 13 Optimal

100 158 217 275 333 392 450 508 567 625 683 742 800 450

87248 133864 172628 210839 248915 284391 319867 352602 368934 376514 380440 380440 380440 319867

11% 18% 23% 28% 33% 37% 42% 46% 48% 49% 50% 50% 50% 42%

3653 4871 6037 7171 8283 9378 10460 11531 12594 13649 14698 15741 16779 10460

293 391 484 575 665 752 839 925 1011 1095 1179 1263 1346 839

288 442 570 696 821 938 1056 1164 1217 1242 94 101 108 1056

-5 51 85 120 157 186 216 238 207 147 76 -8 -91 216

0.0034 0.0029 0.0028 0.0027 0.0027 0.0026 0.0026 0.0026 0.0027 0.0029 0.0031 0.0033 0.0035 0.003

0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.0033

13 11 11 10 10 10 10 10 10 11 12 13 13 9.9

Number

Collector area [m2]

Solar contribution [MJ]

Solar contribution [%]

Energy price fossil fuel [€/MJ]

Simple pay out time [years]

Investment costs [€]

Capital costs [€/year], annuity on investment

Exploitation benefits [€/year]

Equivalent energy price saved energy [€/MJ]

Savings [€/year]


The final results for the optimal solar drying system are summarized in the table below

(see spreadsheet – step 8).

The application of a solar drying system for drying and conditioning of flower bulbs

seems technically and economically feasible.

A solar contribution of 42% can be realised and the pay back time amounts to 10 year.

The net exploitation benefits amount to 216 €/year.

Step 8: Final results

Situation Month Demand Solar contribution

Latitude 52 º [MJ] [MJ]

Orientation 0 º Jan 0 0

Inclination 20 º Feb 0 0

Mar 0 0

System characteristics Apr 0 0

Collector type unglazed collector May 0 0

Collector efficiency 35% Jun 51411 25705

Collector area 450 m2 Jul 203217 92375

Solar contribution 319867 MJ Aug 201997 82963

Solar contribution 42% Sep 170280 58474

Investment costs 10460 € Oct 92993 39858

Capital costs 839 €/year Nov 30991 15495.48

Energy savings 1056 €/year Dec 9990 4994.88

Net exploitation benefits 216 €/year Total 760879 319867

Equivalent energy price saved energy 0.003 €/MJ

Energy price fossil fuel 0.003 €/MJ

Simple pay out time 10 years

0

50000

100000

150000

200000

250000

Ja

n

Fe

b

Ma

r

Ap

r

Ma

y

Ju

n

Ju

l

Au

g

Se

p

Oct

No

v

De

c

Month

En

erg

y [

MJ]

Demand [MJ]

Solar contribution [MJ]


4 Integral approach

The use of energy for drying purposes is in general meant to save drying costs, primary

energy and reduces CO2 emissions. With this in mind it is good to evaluate the total dry-

ing process in relation to energy savings options. A good method for this is the so-called

‘trias energetica’ which basically is a guideline for the prioritisation of ways to reduce

energy consumption.

Step 1: Reduce the energy demand

Energy that is not needed does not have to be generated. Points of interest in this first

step are reducing the drying temperature, reducing the ventilation rate, reduction the

length of circulation pipes for the heating system, lowering thermal losses by insulating

the circulation pipes and use heat recovery. Keep in mind that for some products mini-

mum drying temperatures are needed, and for some products minimum ventilation rates

are needed. Reduction of the ventilation rate can also save a lot of energy needed for the

ventilators.

Step 2: Use sustainable energy

Preferably we should only use sustainable energy for the remaining energy demand. So-

lar thermal energy by means of air collectors is normally well suited for drying applica-

tions.

Step 3: Use fossil energy in the most efficient way

Sustainable energy is not always available. Solar energy resources are dependent from

the time of the day and the time of the year. So fossil energy is needed for back-up heat-

ing. Back-up heating should be done in the efficient way, for example: condensing natu-

ral gas boilers or high efficient gas fired air heaters. Note: for some products the drying

process in not very critical, meaning that during the night the product can be ventilated at

a lower temperature or even by unheated air.


5 Conclusions

A significant number of solar drying plants have been built throughout Europe (some

4000) with a total solar drying collector surface area of more than 1,2 million m2. The

majority of the plants (and 80% of the collector surface) have been built in Switzerland

for forage drying. Furthermore sewage drying on a large scale has come up recently quite

strong (110,000 m2).

Although solar drying systems in general are self made system or integrated in the build-

ing process of new build barns there are some manufactures/suppliers active throughout

Europe. SolarWall sells perforated air collectors, Grammar Solar glazed and unglazed air

collectors, ICT Anlagebau and Thermo-system greenhouse solar dryers and Innotech so-

lar tunnel dryers. Mostly these suppliers are selling their system in a broader sense. As

well in products to be dried (like sewage) as well in application non-drying (pre-heating

of ventilation air).

Monitoring projects show that solar contributions of 50-100% are feasible depending on

product and type of solar drying system.

A simple spreadsheet tool has been made to estimate the optimum size and the economic

feasibility for a solar air collector drying systems. The tool is based on monthly values

and is meant for a first indicative feasibility analysis.

Some guidelines have been compiled in order to stimulate an integral design approach for

the planning of solar drying systems. A short description of the so-called ‘trias ener-

getica’ approach has been introduced for this purpose:

1. Reduce the energy demand

2. Use sustainable energy

3. Use fossil energy in the most efficient way


References

1. Carpenter, S. and R.G.J.H. Voskens (1999). Potential for solar drying in the world.

Enermodal/Ecofys, Kitchener, Canada/Utrecht the Netherlands.

2. Rhonealpenergie (1992). Solar Drying of Agriculture Produce in Europe. EU

THERMIE program action Nº SE 22, France.

3. Bael, J. van, J. Stoobants, and T. Daems (2001). ANRE-Demonstratieproject: Zonne-

daksysteem bij zaadverwerkingsbedrijf Daso, Brugge. (in Dutch) VITO, Belgium.

4. Schröpf, S. and G. Renner (1998). Solar drying plant for biofuels. Grammer Solar,

Germany.

5. Voskens, R.G.J.H., P.G. Out and C.J. van der Leun, (1997). Demonstration project

“De Noord I”; solar energy for the conservation of flower bulbs, results of the moni-

toring data of 2 seasons (in Dutch). Ecofys Utrecht, the Netherlands.

6. Voskens, R.G.J.H. and A. Bos, (2001). Demonstration project “De Noord II”; solar

energy for the heat treatment of Hyacinth bulbs, results of the monitoring data of 2

seasons (in Dutch). Ecofys Utrecht, the Netherlands.


Appendix A

Overview of 3 climate regions and principle crops in Europe (source [1])


1) NORTHERN EUROPE

Region Includes: Norway, Finland, Sweden, Denmark, Germany , The Netherlands,

Belgium, Luxembourg, The United Kingdom and the Republic of Ireland.

Climate: Northern Europe experiences a typical maritime climate with relatively mild

temperatures and abundant well distributed rainfall. Winter temperature become more

severe inland frequent rainfall and moderate temperatures The cropping season begins in

April or May and can end for some crops, such as cereals, in July and August while oth-

ers, such as squash are harvested in late September and October. The solar radiation is

quite low throughout the year though reaching sufficient high levels in summer time.

Principal Crops Include: Cereals; barley, maize, rye, oats. Roots & Tubers: potatoes.

Pulses: dry beans, dry peas. Fruits; apples. Vegetables: various.

Crop Calendar

Irradiation MJ/m2/day 1.9 4.3 8.1 13.0 16.7 18.7 17.0 14.4 10.5 5.9 2.3 1.5

Crops Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Barley

Maize

Rye

Oats

Dry beans

Dry peas

Apples

Vegetables

Potatoes

Drying Methods: Local farmers are drying their products in batch or continuous drying

processes. Approximately 30% up to 60% of the various crops are retained at the farmer

level.

Comments: A market for solar dryers already exists as various solar drying systems have

been used in the past years, as the local governments and the European Government have

funded much research into solar energy applications and the region as a whole embraces

its use, . Among other crops, cereals, hay, vegetables, wood, beans and fruit are solar-

dried


2) CENTRAL EUROPE

Region Includes: Albania, Bosnia Herzg., Bulgaria, Croatia, Czech Republic, Hungary,

Macedonia, Poland, Romania, Slovakia, Slovenia and Yugoslavia

Climate: Most parts of Central Europe experience a continental climate, with wider an-

nual ranges in temperatures between winter and summer. Especially during winter time

temperatures can be severely below the freezing point during a considerable period of

time. The average precipitation is moderate compared with the higher precipitation in

Northern Europe. The Southern part of Central Europe, i.e. Albania, Bosnia Herzg, Croa-

tia and Macedonia experiences a typical Mediterranean climate, which is characterized

by mild temperatures, summer droughts and clear skies. Rainfall is limited and occurs

particularly in autumn and spring. Winter temperature between 7-9 ºC during and sum-

mer temperatures around 23 ºC

Principal Crops Include: Cereals: wheat; rice, barley, maize, rye, oats. Roots and tu-

bers; potatoes. Pulses: dry beans, dry peas, and vetches. Oil crops: sunflower. Fruits:

apples, plums, grapes. tree nuts: walnuts.

Crop Calendar



Wheat

Rice

Barley

Maize

Rya

Oats

Dry beans

Vetches

Sun flower seed

Apples

Plums

Grapes

Potatoes

Walnuts

Drying Methods:

Comments: The market for solar dryers is not quite developed although some solar dry-

ing systems have been used in the past years, as the local governments have funded re-

search into solar energy applications. Among other crops, cereals, hay, vegetables and

fruit could be suitable for the dissemination of solar-dryers.


3) SOUTHERN EUROPE

Region Includes: Austria, Spain, Portugal, France, Italy, Greece

Climate: Southern Europe experiences partly a typical Mediterranean climate, which is

characterized by mild temperatures, summer droughts and clear skies. Rainfall is limited

and occurs particularly in autumn and spring. Winter temperature between 7-9 ºC during

and summer temperatures around 23 ºC. The Northern /Eastern part of Southern Europe

undergoes variable continental influences with a wider range in temperature and espe-

cially colder winters. There are more days of frost and rainfall (whose maximum is in

summer). In the North/Western part of this area the oceanic influences exercises its effect

deep into the area, precipitation is relatively high and temperatures are medium i.e. Win-

ter temperatures are around 5 ºC and Summer temperatures around 17 ºC.

Principal Crops Include: Cereals: barley, maize, rye, oats. Oil crops: sunflower seeds,

rapeseed, linseed. Fruits: oranges, apples, grapes. Roots and tubers: potatoes. Tree nuts:

chestnuts, hazelnuts.

Crop Calendar



Barley

Maize

Rye

Oats

Sunflower seed

Rapeseed

Linseed

Oranges

Apples

Grapes

Potatoes

Hazelnut

Drying Methods:

Comments: A market for solar dryers already exists as various solar drying systems have

been used in the past years, as the local governments and the European Government have

funded much research into solar energy applications and the region as a whole embraces

its use. Among other crops, cereals, vegetables, tobacco and fruit are solar dried.


Appendix B: Contacted experts and organi-

sations

1) Lund, Peter (Prof.), Helsinki University of Technology, Professor, Advanced Energy

Systems, P.O. Box 2200, Helsinki, Finland, FIN-02015, Tel(358.9.4513197),

Fax(358.9.4513195), e-mail([email protected])

2) Müller, J., Hohenheim University, Institüt for Agrartechnik in den Tropen und Sub-

tropen, GarbenstraBe 9, Stuttgart, Germany, D-70599, Tel(49.711.4592490),

Fax(49.711.4593298), e-mail([email protected])

3) Gerd Renner, Grammer, Solar Luft Technik. Wernher-von-Braun-Strasse 6, D-92224

Amberg, Germany. Tel(+49.9621.601-152), Fax(+49.9621.601-260, e-

mail([email protected])

4) Albert Esper, Innotech Ltd. Leanberg, General Manager, Branderburger Street 2,

Leonberg, Germany, D-71229, Tel(49.7031.744741), Fax(49.7031.744742), e-


5) Ulrich Luboschik, IST Anlagenbau GmbH, (manufacturer), Rittenweg 1, D-79400

Kandern-Wollbach, Germany, Tel(+49.7626.91.54-17), Fax(+49.7626.9154-30), e-

mail([email protected]).

6) Werner Weiss, Arbeitsgemeinschaft Erneuerbare Energie, Feldgasse 19, Gleisdorf,

Austria, Tel(+43.3112.5886.17), Fax(+34.3112.5886.18, e-mail ([email protected])

7) Urs Wolfer, Bundesamt für Energie, Worblentalstrasse 32, Bern Switzerland,

Tel(+41.31.3225639), e-mail([email protected])

8) Jean-Luc Bochu, Solagro, 75, voie du TOEC, Toulouse, France,

Tel(+33.567.69.69.69), Fax(+33.567.69.69.00, e-


9) Tilo Conrad, Thermo-System, Echterdinger Str. 57, Filderstadt-Bernhausen, Ger-

many, Tel(+49.711.48945.90) Fax(+49.711.489459.90) email(info@thermo-

system.com)

10) Robert Seidemann, SolarWall, Hetjershäuser Weg 3a, Göttingen, Germany,

Tel(+49.551. 95824), Fax(+49.551.95899), email([email protected])


11) Rick Vases, DLV Bloembollen Tel (+31.6.538.19.772) the Netherlands

12) Riccardo Battisti Assolterm Italy Tel(+39.349.427.7098),

email([email protected])

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