Open Journal of Applied Sciences, 2012, 2, 153-162
doi:10.4236/ojapps.2012.23022 Published Online September 2012 (http://www.SciRP.org/journal/ojapps)
Development and Evaluation of an All Weather-Type
Solar Drying House to Make for Wood Pellet Material*
Kimio Kanayama1, Shinya Koga2, Hiromu Baba1, Tomoyoshi Sugawara3
1Kitami Institute of Technology, Kitami, Japan
2Kyushu University, Fukuoka, Japan
3Marusho-Giken Co. Ltd., Ashoro, Japan
Email: kmkana@bridge.ocn.ne.jp
Received July 16, 2012; revised August 18, 2012; accepted August 28, 2012
ABSTRACT
To suppress the global environment pollutions, we tried to develop a new-type solar drying house by improving a typi-
cal agricultural green-house, so that an all weather-type solar drying house was invented ultimately. This house is capa-
ble to dry raw wood materials (Ogako) into suitable moisture content (Mc) to make a wood pellet. The all weather-type
solar Ogako drying house is covered with a triple transparent film, and an open/close free-type shield sheet is spread
along with house’s inner surface with a small space, which is opened when solar radiation is incident on the house in
daytime and closed to prevent heat loss from the house while out of sun shining in night. Inside of the all weather-type
solar Ogako drying house, there are four belt-conveyors over which four top radiation panels are hanged, and on which
four Ogako agitators are touched, a turn-table, two hoppers, four small fans, and besides, a floor heating is molded in
concrete floor. Also on the north wall outside the house, two insulated cylinders (chimney) are stood up vertically to
exhaust inside moist air passively. Then, to make clearly the operation performance of the house, the drying tests for the
proof examination were conducted nineteen times at first test site in Ashoro where is located east-central part of Hok-
kaido, Japan. As a result of the drying test for the proof examination, it was made clear that the all weather-type solar
Ogako drying house is practically useful as a supplementary apparatus to produce the dried Ogako, and consequently to
suppress CO2 exhaustion.
Keywords: Solar Energy and Biomass Energy; Agricultural Green-House; Ogako Drying House; Wood Powder
(Ogako); Wood Pellet; Moisture Content (Mc); Decrease of Oil Consumption; Suppression of CO2
Exhaustion
1. Introduction
In order to suppress global warming by minimizing the
dependence on nuclear energy, an efficient utilization of
waste materials from a primary industry, such as agri-
cultural fields, forestry and fisheries, has been greatly
attended as the renewable energy resources. One of such
practical uses is a biomass energy of several sorts of
waste wood as a heat source instead of fossil fuels. Re-
cently, the demand for wood pellets made from dried
Ogako has rapidly been increased as a heat source, the
trend has been accelerated greatly. Although wood chips,
planer shavings and barks, in addition to saw dusts, are
useful as raw materials for wood pellet, however, the
moisture content, Mc, has to be severely controlled on
11% ± 1% [1] (wet base: WB) to make the wood pellet
with a press-type pelletizer. While, the wood materials,
especially green wood materials are generally moisture
rich under natural conditions, therefore, the raw wood
materials have to be dried until suitable Mc as mentioned
above. Indeed, artificial drying apparatus (e.g., an air
suction-type drying machine or a kiln-type drying ma-
chine) used usually in the industry, consumes a large
amount of fossil oil and electric power. Therefore, to
decrease the dependence on the fossil oil and electric
power as much as possible, an aggressive research under
a theme of “Developing research of solar Ogako drying
apparatus” was started as a national project from 2005 to
2007 F.Y., which was supported financially from the “New
Energy and Industrial Technology Development Organi-
zation” (NEDO). Consequently, by improving greatly a
traditional green-houses which has been used in agricul-
ture fields, a new type of solar Ogako drying apparatus,
assisted by auxiliary heat partially, could be invented and
developed [2-6]. The objective of this paper is to explain
the outline a new model of “all weather-type solar Ogako
*This research is a part of the project supported by the New Energy and
Industrial Technology Department Organization (NEDO), Japan.
Copyright © 2012 SciRes. OJAppS
K. KANAYAMA ET AL.
154
drying house” [7] and to evaluate the operation perform-
ance undergoing the drying tests for the proof exami-
nation [8-10].
2. Principle and Structure of the “All
Weather-Type Solar Ogako Drying
House”
2.1. Outline
The model of the all weather-type solar Ogako drying
house improved from a typical agricultural green-house
looks like a Quonset hut (Photo 1). The dimensions of
the house are 5.0 mW × 16.0 mL × 3.4 mH. To keep the
shape of house’s body against any external force, e.g., a
strong wind or a heavy snowfall, a frame of the house is
made of steel pipes stood in a concrete floor, on which a
triple transparent film is covered to hold an external form
of the house. Inside the house an open/close freetype
shield sheet is spread along the pipe’s skeleton keeping
with a small the space to control the incidence of solar
radiation (SR) and heat loss depending on a day and a
night. Also inside the house, there are several instru-
ments, such as beltconveyors, turn-tables, agitators, small
fans, hoppers, top radiation panels, floor heating, and as
well as the shield sheet. On the north wall outside the
house, two insulation cylinders (chimney) are set up ver-
tically. Moist air yielded when drying Ogako inside the
house are naturally exhausted through the cylinders due
to a draft force caused by temperature difference between
the inside and the outside of the house.
2.2. Schematic Structure of the House in Detail
The drying house was further improved step by step from
the initial stage of the development. First, the film cov-
ered over the house was changed from a double-style to a
triple-style, next the exhaustion of the moist air inside the
house was performed by a ventilation fan and a dust
blower actively, and then done by an insulated cylinder
Photo 1. Outside view of the all weather-type solar Ogako
drying house.
passively. The final status of the main body of the house
[7] is as follows: Figure 1(a) shows a front view of the
house, and Figure 1(b) shows a plan figure of the house.
The outside of the house is covered by a triple tran-
sparent film, and inside of the house there are several
parts, goods, and other instruments. For example, they are
four belt-conveyors set on a rack frame, four top radiation
panels hanged from an overhead frame, two hoppers at
3400
5000
5000
2400
Insulated cylinder×2
Passiveexhaustion
Fold-typeshield sheet
Small fans
(
25W×4
)
Roll-type
shield sheet
shutter
windows
At night
In daytime
Over-
head frame
South
Take-in
damper duct
Top radiation
panel
T
ake-out
d
amper duct
Ogakoreturen
table
Supply-hopper
Recovery hopper
Goahead-Conbeyor
Concrete floor
(black colored)
Floor heating
Depth:16m
Return-Conbeyor
Triple transparent film
φ300mm
(a)
3400
5000
10000
16000
14000
Goahead conveyor
Topradiation panel
(Removable)
(Fixed)
Returnconveyor
Supplyhopper
Recovery
hopper
Ogako return
table
Insulatedcylinder
Take-in Damperduc
t
Take- out
damper duct
Take-in
damper duct
Small fan×4
Shutter window
Entrance
4200
South
Floor heating
(Removable)
(Fixed)
Shutter window
(b)
Figure 1. (a) Front view of the Ogako drying house; (b)
Plan of the Ogako drying house.
Copyright © 2012 SciRes. OJAppS
K. KANAYAMA ET AL. 155
supplying and recovering places for the Ogako powder, a
turntable at back part of the house, four small fans set on
the overhead frame, a floor heating system molded in the
concrete floor, two damper ducts, two shutter windows,
and as well as an open/close free-type shield sheet. Out-
side the house, two insulated cylinders (5.0 m height, φ
300 mm) are stood vertically to exhaust passively moist
air from the house through the damper ducts fixed in the
under part. Additionally, the panel wall on the west side
of the house has an entrance with a double door covered
by the triple transparent film too.
2.3. System Operation and Ogako Drying
Process in the House
Referring to Figures 1(a) and (b), firstly, before operat-
ing the system, the floor heater and top radiation panels
are heated by feeding hot water (50˚C - 60˚C) and steam
(160˚C - 170˚C), respectively. Secondly, on the fine day,
the house receives a lot of SR, and approximately 50
percent of the SR is collected in the house as solar heat
[9,10], and a part of which is incident directly upon the
Ogako on the belt-conveyors fed from a supply hopper.
While the Ogako is slowly moving, the moisture is
evaporated little by little. Temperature and moisture in-
side the house are kept at suitable levels, and the Ogako
is dried gradually with absorbing SR directly, and with
receiving indirectly low temperature radiation (infrared
radiation) within the enclosed house being kept in “a
quasi-radiation cavity” [9,10]. Next, the mostly dried Ogako
is recovered into a receiving hopper from a return-con-
veyor after being carried with a go-ahead conveyor through
a turn-table taking 80-95 minutes in total. When operat-
ing the system, four small fans on the over-head frame
are worked to blow a breeze for acceleration of Ogako
drying, and four Ogako agitators on each four separated
belt-conveyors are also worked to rotate for Ogako mix-
ing in order to dry as speedy and uniform as possible. At
the same time, by opening the damper ducts fixed in un-
der part of two insulated cylinders, the moist air inside
the house is exhausted to the outside passively, and in
collaboration with that, the two damper ducts fixed in the
east and west panel walls of the house take in dry air into
the house by opening damper in proportion to SR inten-
sity. The width of the belt-conveyor is 900 mm (effective;
850 mm), the depth of the Ogako layer is 30 mm or 50
mm which is changed corresponding to the conveyor’s
speed which is ranged between 0.232 - 0.275 m/min.
2.4. Delivery and Receive for Solar Radiation
and Heat inside and outside the House
Figure 2 shows the schematic of the delivery and receipt
of ray and heat from SR on the drying house, and heat
from the auxiliary heat source a fine day. The global SR
Depth
;16m
T
in
:
Inside Temp.
T
out
Outside Temprature
H
out
Outside Humidity
I( Q)
VI
Volumetric S.R. Incidence
T
fl
:
Surf.Temp.
of F.H.
Quasi-Radiation Cavity
due toS. R. mainly
Skeleton
Frame
Transp.S.R.
Reflection Lossof
TramsmittedRay
Floor Heating
Convection Loss→
small
Reflection Loss of
Tramsmitted Ray→small
Retransmitted
Lossof
Direct
Tramsmitted
Ray→middle
ExhaustLoss→large
F.Surf. of
Black Color
Triple Transparent
Film
Heat Lossinto
Earth→very small
Scattering
S. R.
Scattering S.R.
I( Q)
VI
Reflect.
S. R.
Hin; InsideHumid.
Figure 2. Heat balance of the Ogako drying house covered
by a triple transparent film on day-time; “Quasi-radiation
cavity”, which is less efficient than night-time in its self, as
Figure 3.
(i.e., Total SR = Direct SR + Scattered SR + Reflected
SR) is incident three dimensionally around the house as
the volumetric SR incidence I (Q)VI. The direct and scat-
tered components of the global SR are transmitted through
a triple transparent film and a space of the skeleton frame
into the house. The SR is incident upon Ogako layers on
the conveyors and the Ogako particles on the other places
directly, and thus the moisture contained in the Ogako
powder is evaporated. Moreover, the Ogako is heated
directly by an infrared radiation from the top radiation
panels ( 150˚C), and also heated indirectly with infra-
red radiation of low temperature (50˚C - 60˚C) within “a
quasi-radiation cavity” [10] filled with the other random
infrared radiation from the top radiation panels and the
floor heating. Therefore, under a good sunshine day, the
top radiation panel over the go-ahead conveyor is moved
north side to allow the incidence of SR directly on the
Ogako layer. The evaporated water yielded due to the SR
and the auxiliary heat is forced forward two damper
ducts and exhausted outside as moist air through an in-
sulated cylinder, and instead of that, dry air are taken in
the house from the outside. The direct and scattered com-
ponents of the SR incident upon the house, are passed
through the triple transparent film and the space of
skeleton frame as a ray, converted into heat partially, and
absorbed by Ogako and other materials as heat. However,
a part of SR incidence of which leaves from the house as
a ray alone directly and reflectively, which is caused to a
heat gain loss, and moreover, there are several heat
transfer losses from the house surface. Where, the largest
one of the heat loss is an exhaust heat loss blowing from
the insulated cylinder. Therefore, the collecting ef-
ficiency of the volumetric SR incidence is roughly 50%,
which is estimated from the result on a hot house covered
Copyright © 2012 SciRes. OJAppS
K. KANAYAMA ET AL.
156
by a triple transparent film and a CF-sheet [8-10]. Fig-
ure 3 shows the schematic of the delivery and receipt of
infrared radiation from the auxiliary heat at night. This
schematic is very similar to Figure 2 for a fine day, ex-
cept that there is no incidence of SR and the shield sheet
is closed over the inner surface of the triple transparent
film entirely. High temperature steam is fed to all the top
radiation panels continuously, and the panels emit infra-
red radiation to the Ogako on the conveyor during the
transfer. Therefore, we can dry raw Ogako in the Mc of
approximately from 30% - 40% to 10% or less even if at
night. During the night, the inside of the house can be
maintained nearly “a quasi-blackbody radiation cavity”,
filled with infrared radiation. The house closed shield
sheet in night is relatively efficient due to this “cavity
effect” [10] in comparison with a normal house of open
shield sheet on a fine day.
3. Experimental Methods
3.1. The Ogako Drying Test for the Proof
Examination
The Ogako drying tests for the proof examination using
the all weather-type Ogako drying house were conducted
nineteen times at Ashoro (43˚145'N, 143˚33.5'E), Hok-
kaido, Japan, from 2005 to 2007 F.Y. According to the
meteorological data of the Ashoro site from 2007 [11,
12], the annual averaged temperature, daily maximum
temperature and daily minimum temperature were 12.5˚C,
35.6˚C and –20.2˚C through a year, respectively. The
average precipitation a year was 636 mm with 1949.1 h
of annual sunshine hour. The Ogako (wood powder)
made of fresh Japanese larch tree with a wood chipper
was provided as the test material. The size of the powder
was less than 8 mm totally (less than 0.5 mm: 4.2%, 0.5 -
1 mm: 7.5%, 1 - 2 mm: 32.2%, 2 - 4 mm: 53.5%, 4 - 8
mm: 2.6%), and so the Mc was ranged from 22 to 44%.
A few tests of the 19 runs of drying test were abandoned
because of system adjustment alone or a lack of useful
measurements. As a total, the nine drying tests for the
proof examination, i.e., No. 1 to No. 9, for daytime and
night through a year are selected (Table 2) for the analysis.
3.2. Monitoring the Drying Process of Ogako
On the nine drying tests for the proof examination, the
conveyor’s width was 900 mm (effective; 850 mm), the
depth of the Ogako layer was 50 mm, and the speed of
the conveyor was around 0.27 m/min for the drying test
No. 1 to No. 4. While, after drying test No. 5, the depth of
Ogako on the layer was 30 mm, and the conveyor speed
was around 0.23 m/min. The time to produce a dried
Ogako takes 80 min to 95 min every one round. The belt
conveyor was consisted of two lanes with two short con-
veyors of 5 m length in each lane, so that length of the
Ogako layer equals nearly the conveyor’s distance plus α.
Figure 4 shows the sampling places and the times for
Ogako specimens while the Ogako was slowly flowing
on the belt conveyor for the drying test No. 5, as an ex-
ample. Length of two lanes including a half circular lane
of a turn table was 22 m in total. Every one of four short
conveyors had one agitator to mix the Ogako powder.
The Ogako sampling was performed as follows: The first
spooning at place 1 is at time 0 min; once the process
started, the second spooning occurs at place 2 in 15 min
after the start; the third spooning at place 3 occurs in 40
min after; the fourth spooning at place 4 occurs in 70 min
T
in
:Inside Temp.
T
out
Outside Temperature
H
in:
Inside Humid.
H
out
Outside Humidity
T
fl
:
Surf.Temp. of
Floor Heating
Quasi-Blackbody
Radiation Cavity
Frame
Floor Heating
Convection
Loss→small
Exhaust Loss→large
Floor Surf. of
Black Color
Triple Transparent Film
Heat Loss into
Earth→very small
ShieldSheet
RadiationLoss
→very small
Tst:T emp.
Shield
-s heet
(≒Tin)
Depth
;16
Figure 3. Heat balance of triple transpa rent film Ogak o drying
house when closing shield-sheet in night; “Quasi-blackbody
cavity”, which is more efficient than daytime in its self, as
Figure 2.
Turn Table
after45min.
Place4:
after 70 min.Place2:
after15min.
Place 3:
after 40 min.
Start of Sampling:
Place 1:0 min.
Finishe d
Place5:after90 min.
Return Conveyor
Go-ahead Conveyor
Agitator 2
Agitator 1
Agitator 3
Agitator 4
Figure 4. Time of elapse and place for sampling of Ogako
drying test No. 5, as an example.
Copyright © 2012 SciRes. OJAppS
K. KANAYAMA ET AL.
Copyright © 2012 SciRes. OJAppS
157
after; and the last fifth spooning at place 5 occurs in 90
min after. In other words, the Ogako layer after the first
spooning at place 1 goes to the next sampling place 2 in
15 min after, and the second sampling occurs. The pro-
cedure is repeated for places 3 and 4, until the last sam-
ple is taken at place 5 in order, so that the sampling pro-
cedure is completed when 90 mim elapsed. The first
round for sampling starts at 10:15, after just one hour the
second round of sampling is performed, and thus the
sampling is continued every one hour, until eight rounds
are finished or seven hours passed. The mass of the
Ogako powder for each sample was 30 to 60 g, and the
sample is taken from the upper and lower both levels of
the Ogako layers at each place. The weight of each
specimen is measured immediately. Then, the difference
in the specimen weight between before and after being
oven-dried was measured, and the Mc could be calcu-
lated in terms of wet-base (WB).
every tilt angle and azimuth angle obtained from the da-
tabase of the Japan Weather Association (JWA) [11,12].
The logical procedure is based on a conventional calcula-
tion method adopted on “the fully passive solar lumber
drying house” in the previous paper [8]. From the data-
base, we obtained the intensity of the SR incidence on
each surface of the house multiplying it by the surface
area. The products were summed up on the each surface
after integrated over the time from sunrise to sunset.
From this procedure, we can calculate the volumetric SR
incidence I(Q)VI MJ/day. By multiplying the I(Q)VI by
0.5 which is the collecting efficiency of the volumetric
SR incidence, the volumetric solar heat collected per day
QVC (MJ/day) can be calculated.
Thus the efficiency of volumetric solar heat collected,
ηVC, is defined as the ratio of QVC to the SR incidence on
a floor area I(Q)fl. The efficiency of volumetric solar
heat collected, ηVC, is larger in winter and smaller in
summer than the yearly average value. As shown in Fig-
ure 5, these performance factors are calculated when the
house is operated. From the results in Figure 5, we can
see 113.3% maximum in Jan., and 71.3% minimum in
Jun. with a yearly average of 82.7%. In other words, the
4. Results and Discussion
4.1. Estimation of the Operation Performance
Table 1 indicates the SR incidence on a tilt surface for
Table 1. Tile surface SR on floor, East, South, West surfaces averaged a month and a year at Ashoro (43˚145'N, 143˚33.5'E).
Tilt angle θ Azimuth Angle α Jan. Feb. Mar.Apr.May.Jun.Jul. Aug.Spt.Oct. Nov. Dec.Year
θ = 0˚, α = 0˚; Floor surface 6.77 10.15 13.86 15.91 17.75 17.88 15.8813.8215.22 9.83 6.7 5.5412.17
θ = 90˚, α = 0˚; South surface 13.46 15.84 14.18 10.338.938.327.977.998.93 11.23 10.91 11.16 10.96
θ = 90˚, α = –90˚; East surface 5.80 8.78 9.299.3610.229.97 8.88 7.70 7.02 6.44 4.68 4.397.70
θ = 90˚, α = 90˚; West surface 5.80 8.78 9.299.3610.229.97 8.88 7.70 7.02 6.44 4.68 4.39 7.70
Performance Estimation of Ogako Drying House
(
Ashoro
)
0
500
1000
1500
2000
2500
MJ/d, %
Horiz. Total S. R. incidence; I(Q)HT=I(Q)fl541.4812.21108.81275.81419.8 1428.51270.1 1105.9941.8786.2535.7443.5973.4
S. R. incidence on floor; I(Q)fl=I(Q)rf541.4812.21108.81275.81419.8 1428.51270.1 1105.9941.8786.2535.7443.5973.4
S. R. incidence on South Wall; I(Q)ws517.0 608.3544.7396.7342.8319.3305.5306.9342.8431.3418.9428.5413.3
S. R. incidence on East/West Wall;
I(Q) w e/ww
168.1254.7 269.4271.4 296.5 289.2255.8 223.4203.6186.9 135.7 127.4223.4
Volumetric S. R. incidence; I(Q)VI1226.51675.2 1922.91943.62059.12037.0 1831.4 1636.21488.2 1404.4 1090.3 999.41610.1
Volumetric S. R. Collected; QVC613.3837.6961.5971.81029.61018.5915.7 818.1744.1 702.2545.2499.7805.1
Rate of Volumetric S. R. incidence; ηVI226.5206.3173.4152.3145.0 142.6144.2148.0 158.0 178.6204.3225.3165.4
Rate of Volumetric S. R. Collected
;
η
vc113.3103.286.776.272.571.372.174.0 79.0 89.3102.2112.782.7
Jan.Feb. Mar.Apl.MayJun.Jul.Aug. Sep.Oct.Nov. Dec.Year
Figure 5. SR incidence on floor, roof, and every wall, and volumetric SR incidence and also the rate of volumetric SR col-
lected.
K. KANAYAMA ET AL.
158
collection magnitude as solar heat vs. the SR incident
upon the floor area as a ray are in Jan. 1.13 times, in Jun.,
0.713 times and in yearly average, 0.827 times of the SR
incidence on the floor area. These performance factors
are estimated as an averages per month or per year,
therefore, they only represent the identified factors as a
standard index of the operation performance when the all
weather-type solar Ogako drying house operates at Ashoro
site only.
4.2. Results of the Drying Tests for the Proof
Examination
The primary results of each drying test for the proof ex-
amination are shown in Table 2. From this table, Figure
6 shows the temperature and humidity inside and outside
the house to illustrate the trend of measurements. The
temperature inside the house was lower in winter and
higher in summer than the average temperature of 50.4˚C.
This temperature is roughly in proportion to the outside
temperature, and the difference between both tempera-
tures through the year was approximately 15˚C - 20˚C.
Figure 7 shows the amount of heat supplied by the
auxiliary heat and the volumetric solar heat collected QVC.
Furthermore, a ratio of the volumetric solar heat col-
lected to the total heat supply, namely, the solar heat
fraction, Fs, is also shown in Figure 7. The supplied heat
was larger in winter for the drying test No. 2 and smaller
in summer for the drying tests No. 8 and No. 9. The Fs
during operating the system was 40% - 65% on a fine
day, but on cloudy days it decreased in 20% - 30%, and
in night it was entirely zero.
Table 2. The results of “Ogako drying test” at Ashoro site for the proof examination during 2006 to 2007.
No. of drying test No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 No. 7 No. 8 No. 9
Date and time Oct. 27, '06
10:00-17:30
Dec. 5, '06
15:30-22:30
Feb. 20, '07
10:00-19:30
Apl. 17, '07
10:00-17:00
May 29, '07
10:00-17:30
Jun. 8, '07
18:30-22:30
Jul. 12, ‘07
4:30-10:30
Aug. 23, '07
10:30-14:30
Aug. 23, '07
18:30-22:30
Day/Night Daytime Night Daytime Daytime Daytime Night Daytime Daytime Night
Outside temp., ˚C 8.6 4.1 0.2 5.3 21.3 16.6 11.0 24.7 18.5
Outside humid., % 70.4 79.6 47.6 54.6 36.4 89.0 95.6 50.4 76.3
Inside temp., ˚C 44.1 30.6 48.2 56.6 63.5 48.7 41.0 66.2 54.5
Inside humid., % 18.7 25.7 15.3 12.7 7.5 19.7 24.5 8.6 14.5
Total heat supply, MJ 91.6 137.7 96.8 86.6 89.3 66.8 52.1 38.5 32.9
Auxiliary heat, MJ 78.2 137.3 67.8 47.6 48.2 66.8 47.9 13.6 32.9
S. R. heat, MJ 13.5 0 29.0 39.0 41.0 0 4.2 24.9 0
S. R. heat fraction, MJ 0.15 0 0.30 0.45 0.46 0 0.08 0.65 0
Initial Mc., % 21.6 29.8 35.8 43.5 25.8 28.1 29.9 33.4 34.9
Final Mc., % 6.4 25.3 29.5 25.6 11.3 17.6 20.4 19.6 22.9
Decrement. of Mc., % 15.2 4.5 6.3 17.7 14.5 10.5 9.5 13.8 12.0
Evaporated moist, kg 89.3 61.4 62.6 190.0 73.8 39.4 49.9 57.3 66.5
Raw Ogako handled, m3 7.16 7.16 4.30 4.30 4.30 2.46 3.07 1.84 1.84
Operation period, h 7.0 7.0 9.5 7.0 7.5 4.0 6.0 4.0 4.0
Remarks Fine day Night Fine day
Steam valve
was out of
order in a
moment
Fine day
Night, flow
meter was
out of order
Early
morning
Mainly S. R.,
triple trans.
film
Night in
same day as
left
Copyright © 2012 SciRes. OJAppS
K. KANAYAMA ET AL. 159
Temp. & Humid. of Inside and Outside of theHouse
-20
0
20
40
60
80
100
120
No. 1
day
No. 2
night
No . 3
day
No. 4
day
No. 5
day
No. 6
night
No. 7
early
No. 8
day
No. 9
night
Number of Test
Temp. ℃, Humid. %
Outside Temp. To Outside Humid. Ho
Inside Temp. To  Inside Humid. Ho
Figure 6. Inside temperature and humidity, outside tem-
perature and humidity vs. each number of dry i ng te sts.
Heat supply, Volumetric S. R. Collected and Solar Fractio
n
0
20
40
60
80
100
120
140
160
No.1
day
No.2
night
No.3
day
No.4
day
No.5
day
No.6
night
No.7
early
No.8
day
No.9
night
Number of Test
MJ, %
Total Heat Supply QTHAuxiliary Heat Qaux.
Volumetric S. R. collected QVCSolar R. Fraction FS %
Figure 7. Heat supply of SR and auxiliary heat, and the
solar heat fraction, Fs, for each drying test.
Figure 8 shows the initial Mci, the final Mcf, the dif-
ference in between both, and the water evaporated during
each drying test from No. 1 to No. 9. The difference in Mc
ranged from a few percent to 25%, depending on the
amount of drying time, the intensity of SR, and the set-
tings and controls of all the instruments in the house, and
so forth. After drying test No. 5 with progressive im-
provement, a raw Ogako of initial Mci of 30% - 40%
(WB) decreased by 10 - 20 points in percentage, and so
the dried Ogako with 10% - 20% of Mcf was produced
finally. However, this technique of Ogako drying house
is in the experimental stage still, it needs auxiliary heat to
yield fully and uniformly dried Ogako. As above the
production of an enough dried Ogako could be directly
supplied into a pelletizer to make a fuel pellet. However,
to provide the practical drying house, the simplification
of house’s structure and the operating method, and so the
cost down are required much more. Therefore, the drying
tests so as to grade up the house’s performance have to
be continued under a drying test for the proof examina-
tions with trial and error after this time.
4.3. Details of the Moisture Decrement Every
Round of the Ogako Drying Tests
The apparatus and instruments included in the all weather-
type Ogako drying house and the experimental method of
Ogako drying were advanced gradually along with each
drying test. First, two large fans with shatter for forced
ventilation was removed, and replaced with two insulated
cylinders on the outside the house to exhaust naturally
moist air inside the house. At the middle stage after dry-
ing test No. 5, the total system of the house was arranged
with the double transparent film, a shield sheet, four belt
conveyors and an air blower, including other instruments.
Where, the air blower has a role to take out dried Ogako
actively from the drying house. However, after drying
test No. 8, the air blower was taken out entirely, and the
double transparent film was exchanged with a triple
transparent film to increase the insulation effect from
heat loss of the house.
Figure 9 shows the relation between the Mc decre-
ment and the time elapsed as a result of eight sampling
rounds on the drying test No. 5. The Mc in the first round
of drying when started at 10:15 in place 1 was 22%, and
decreased in 6% by 16 points at last place 5. The subse-
quent rounds of drying continued with just one hour in-
terval until the eighth rounds finished, and so the final
round of drying of the eighth started at 17:15 in place 1,
followed by sampling at places 2, 3, 4, and 5 in order.
The initial Mc of 27% decreased in 15% by 12 points at
place 5. As shown in Figure 10, averaging the operation
trends shown by the eight separated lines on Figure 9,
the drying performance could be clearly drawn by a sin-
gle line. From this Figure 10, the initial Mc of 25.8%
decreased in 11.3% by 14.5 points as averaged, which
were the largest decrement of Mc owing to very fine day.
This recorded result also corresponds to the highest dry-
ing speed of 9.7%/h among the nine drying tests.
Intial & Final Mosit. Content, Decreas of Moist. Cont.
and Evaporated Water
0
10
20
30
40
50
60
70
80
90
100
No .1
day
No . 2
night
No .3
day
No .4
day
No .5
day
No . 6
night
No .7
early
No .8
day
No .9
night
Number of Test
Moist. Cont. Mc %,
E
vaporated Water kg
Initial Moisture Cont. Mci %Final Moisture Cont. Mcf %
Decreas of Moist. Mcd %Evaporated Water kg
Figure 8. Variation of initial and final Mc, decease of Mc,
and evaporated water during drying test.
Copyright © 2012 SciRes. OJAppS
K. KANAYAMA ET AL.
160
0
5
10
15
20
25
30
020406080100
Time of Elapse (min.)
Moisture Content
%
10:15
11:15
12:15
13:15
14:15
15:15
16:15
17:15
OgakoDrying Test No.5
(May 29th '07, 10:00~17:30)
Place1
Place 2
Place 3
Place 4
Place 5
Time of
sampling place1
Figure 9. Time of elapse and Mc on each sampling place on
daytime.
Ogako Drying Test No.5 (May 29th '07;10:00~17:30)
0.0
5.0
10.0
15.0
20.0
25.0
30.0
M
oisture Content (%)
Moi sture Content (%)25.8 23.3 19.1 13.8 11.3 14.5 9.7
Place 1;
0min.
Place 2;
20min.
Place 3;
40mi n.
Place 4;
70min.
Place 5;
90mi n.
Mo is tu re
decr ement
(point)
Drying
speed
(%/h)
Figure 10. Moisture decrement with time of elapse, total Mc
decrement and drying speed when Ogako drying on fine
day.
Similarly, Figure 11 shows the relation between the
Mc and the elapsed time for drying test No. 6 in night.
This figure indicates four rounds of the drying test during
a drying time of 90 min. and the depth of Ogako on the
conveyor of 30 mm. The decrement in Mc after every
sampling round was not so good because the average
temperature inside the house was relatively low of 48.7˚C.
Figures 12(a) and (b) show the relation between the
Mc and elapsed time for drying tests No. 8 and No. 9,
respectively. As shown in two figures, these tests with
three drying rounds each were performed during day and
night on the same day, but between which a time interval
was of four hours. Figure 12(a) shows the result for the
three sampling rounds during the day. Before the drying
tests No. 8 and No. 9, the double transparent film was
exchanged with a triple transparent film, however, the
depth of Ogako of 30 mm and a drying time of 85 min
were kept for each drying round. As shown in Figure
12(b), a drying time every round of the three samplings
took 95 min due to during night. If we represent simply
with a single line averaged instead of three trend lines,
the drying performances shown by Figure 12(a) on day-
time and Figure 12(b) in night become into two trend
lines as shown in Figure 13. From Figure 13, it is clear
Ogako Drying Test No.6
(Jun. 8th, '07; 18:00~22:30
)
0
5
10
15
20
25
30
020406080100
Time of Elapse (min.)
M
ois
t
ur
e
C
on
t
e
n
t
(
%
)
18:00
19:00
20:00
21:00
Place 1
Place 2
Place 3
Place 4
Place5
Time of
sampling place
1
Figure 11. Time of sampling start and Mc on each sampling
place in night.
Ogako Drying Test No.8
(Aug.23rd '07; 10:30~14:30)
0
5
10
15
20
25
30
35
40
020406080100
Time of Ela
p
se
min.
M
o
i
s
t
ure
C
on
t
en
t
(
%
)
11:00
12:00
13:00
Place 1
Place2
Place 3
Place 4
Place 5
Time of
sampling place 1
(a)
Ogako Drying Test No.9
(Aug.23rd '07; 17:30~22:30)
0
5
10
15
20
25
30
35
40
0 20406080100
Time of Elapse (min.)
Moist u
r
e
Cont
e
nt
(
%
)
18:00
19:00
20:00
Place1
Place 2
Place 3
Place 4
Place 5
Timeof
sampling place1
(b)
Figure 12. (a) Time of sampling start and Mc on each sam-
pling place on daytime; (b) Time of sampling start and Mc
on each sampling place in night.
Ogako Drying Test No.8 & No.9
(Aug. 23rd '07;10:30~14:30 & 18:30~22:30)
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
Time of Elapse (min.)
Moisture Content
(
%
)
Daytime 33.4 31.327.322.819.613.8 8.7
Ni
g
ht 34.932.829.825.3 23.0 12.0 7.5
Place 1;
0 min.
Place 2;
20 min.
Place 3;
40 min.
Place 4;
70 min.
Place 5;
95 min.
Moisture
decreme
nt (%)
Dr y i ng
speed
(%/h)
85 min.
95 min.
Figure 13. Mc decrement with time of elapse, total Mc dec-
rement and drying speed for day and night.
Copyright © 2012 SciRes. OJAppS
K. KANAYAMA ET AL. 161
that the initial Mc of the raw Ogako on daytime was
lower than that of night, and the decrement in the Mc on
daytime was 13.8 points after 85 min, which was slightly
higher than the 12.0 points in percentage after 95 min in
night. In this case, therefore, we can result in the drying
speed of 8.7%/h for the day and 7.5%/h for the night.
The speed of the belt-conveyor including a turn table
corresponded to 0.258 m/min for the drying time of 80
min. Connecting with this 0.244 m/min is for the drying
time of 85 min and 0.232 m/min is for the drying time of
95 min. Where, depth of the raw Ogako layer on the
conveyor was 30 mm. As an example of a slow drying
speed, Figure 14 shows the results from Ogako drying
test No. 7 with single averaged for the drying test from
early cloud morning 4:30 to 10:30. The results of 9.5
points in percentage of the Mc decrement, or the drying
speed of 6.0%/h obtained during 95 min. It was not so
good because of cloudy sky from the early morning.
Consequently, the performance factors under the good
conditions could attain the drying speed of 10%/h or
more, during one round as shown on the Ogako drying
tests No. 5 and No. 8, because of the fine days.
5. Evaluation of the Environmental
Preservation
Though the total heat supply in the house is the sum of a
solar heat and an auxiliary heat from fossil oil, when us-
ing wood pellets as a heat source, CO2 exhaustion is con-
sidered to be zero according to the international rule of
carbon neutral base. Therefore, the auxiliary heat system
supplied by the wood materials wholly contributes not
only the reduction in the consumption of fuel oil, but also
the suppression of CO2 exhaustion.
As an example, an eco-feasibility study in this experi-
ment is as follows:
1) Conditions of the calculation:
Rate of operation of the house/year: 60% (= 8760 h ×
0.6 = 5256 h)
Operation hour in daytime/year*: 871.6 h
Ogako Drying Test No.7 (Jul. 12nd '07; 4:30~10:30)
0
5
10
15
20
25
30
35
Time of Elaps
e
Moisture Content
(
%
)
Moisture Content
(
%
)
29.928.326.322.820.49.56.0
Place 1;
0 min.
Place 2;
20 min.
Place 3;
40 min.
Place 4;
70 min.
Place 5;
95 min.
Moi s t ur e
decremen
t (Point)
Drying
speed
(%/h)
Figure 14. Mc decrement and drying speed when Ogako
drying from early cloud morn ing.
Operation hour at night/year*: 4384.4 h
*Operation hours for daytime and night are determined
from energy balance.
2) On the daytime:
Total heat supply: 11.0 MJ/h × 871.6 h = 9561.4 MJ
Auxiliary heat supply:
7.14 MJ/h × 871.6 h = 6223.2 MJ
Solar heat collected:
3.83 MJ/h × 871.6 h = 3338.2 MJ
Ogako handling volume:
0.70 m3/h × 871.6 h = 610.1 m3
3) In night:
Total heat supply:
(14.9 + 0) MJ/h × 4384.4 h = 65327.6 MJ
Auxiliary heat supply:
14.9 MJ/h × 4384.4 h = 65327.6 MJ
Solar heat collected: 0 MJ/h × 4384.4 h = 0 MJ
Ogako handling volume:
0.70 m3/h × 4384.4 h = 3069.1 m3
4) Performance factors/year:
Total heat supply:
(9561.4 + 65327.6) MJ = 74889.0 MJ
Auxiliary heat supply:
(6223.2 + 65327.6) MJ = 62550.8 MJ
Solar heat collected: 3338.2 MJ + 0 = 3338.2 MJ
Ogako handling volume:
610.1 m3 + 3069.1 m3 = 3679.2 m3
Solar heat fraction/year Fs:
3338.2/9561.4 0.35 35%
(daytime only)
Saving of A-heavy oil/year**:
74889.0 MJ/39.1 MJ × 0.8 = 2394.1 L
Suppression of CO2/year***:
2394.1 L × 0.0163 kg-C/L = 39.0 kg-C = 143.1 kg-CO2
**: The value 0.8 is an efficiency of the boiler.
***: The value 0.0163 is a coefficient when converting
A-oil into kg-C.
That is, according to the case study as above and the
experimental results from the nine drying tests for the
proof examination through one year, which consist of six
daytime tests and three night-time tests, the environ-
mental contributions due to “all weather-type solar Ogako
drying house” were as follows:
1) The solar heat fraction through the year, Fs, was
35% for daytime;
2) The savings of A-heavy oil was 2394.1 L per year,
and the suppression of CO2 gas exhaustion was 143.1
kg-CO2 per year.
Copyright © 2012 SciRes. OJAppS
K. KANAYAMA ET AL.
Copyright © 2012 SciRes. OJAppS
162
onsumption and suppress the ex-
uation on the prac-
tic
7. Acknowledgements
artially a result of the “New
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In order to reduce oil c
par
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try, on an “all weather-type solar Ogako drying house”
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for the proof examination was done over nearly three
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mostly. While the drying test was progressed, the drying
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the operation performance was gradually raised up ac-
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From a view point of the total eval
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cellent soft technology useful to overcome this critical
era for the global preservation.
This developing research is p
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