2. 22
Current Energy Uses
• Grid Connected Electricity (PLN)
– Process, Cooling and Utilities.
• Own Steam Generation (PGN)
– Hot water (Sanitation/Production)
– Product Heating (Boiling)
General Way Of Working:
3. 33
Proposed Energy Uses
• Bio-mass gasification/combustion.
• Self Generation by Gas-Engine/turbine
– Electricity
– Hot water + HRSG
• High Temperature Solar Devices
– Cooling (8 or 24 hrs. with storage)
– Steam (with accumulator)
– Hot water (8 or 24 hrs. with storage)
4. Bio-Mass Options
4
Three major energy conversion processes can be considered, I.e.,
•Combustion > Steam > Power Generation and Heat.
•Gasification > Producer Gas > Power Generation and Heat.
•Anaerobic Digestion > Methane > Power Generation and Heat.
Bio-mass, or agricultural waste is in many forms available in Indonesia. More
often than not, much of the bio-mass is discarded or plainly burned on the
fields. The most common types are listed below;
•Rice husk – LHV ~ 14 MJ
•Coconut Shells (Meso/exocarps) – LHV ~ 16 MJ
•Woody Types – Cassava waste – Bamboo waste etc. LHV ~ 18 MJ
•Captive Waste – Saw Dust – Organic waste/effluent etc. LHV varies.
5. Combustion
5
Combustion takes place in a steam generator where the fuel (bio-mass) is
converted into steam of a certain pressure. This conversion can reach a
efficiency of approximately 88%. (Q-in vs. Q-out)
The steam can be utilized in a condensing steam turbine for electrical power
generation, or in a extracting steam turbine for power en heat generation.
The total efficiency is approximately 25% depending on whether a extracting or
condensing approach is followed.
Fly-ash can be an additional income stream while, in case of rice-husk, silica
can be a by-product as well.
As indicated, system efficiency is low, while Capex is considerable, especially
when higher steam pressures (thus higher efficiencies) are employed.
A point of concern is the reliability of feed-stock supply. Although previously
stated, bio-mass is readily available and is often discarded on the field.
However, when a buyer appears, it (the bio-mass) becomes instantly an
commodity. It is therefore important to strike long-term agreements with
communities, private suppliers en local leaders in order to guarantee supply
and price.
6. Gasification
6
Gasification is a process whereby under low oxygen conditions, a combustible
fuel (bio-mass / BM) is converted into a gas that can be used by internal
combustion engines. The process comprises of 4 distinct phases as follows:
•Drying – in order to reach a MC of 10% or lower.
•Pyrolysis – to raise HV by further removing water.
•Combustion – BM is partly combusted to maintain reactor temperature.
•Reduction – BM is converted into gas. (CO + H2 + CH4)
All phases take place in the reactor on different levels. Feedstock is added from
the top, ash is removed from the bottom. The ash can be compressed into
briquette and be considered an additional income stream.
Efficiency of the entire cycle, gasification to generation is of the same order as
a steam process, however, Capex is much lower. Moreover, it is possible to
store gas for later use, which considerably increases flexibility.
7. Anaerobic Digestion
7
Digestion is a biological process whereby methanogenic bacteria convert an
organic waste into methane (CH4) in a anaerobic atmosphere. The process
takes place in a ‘digester’ which can be ‘plug-flow’, a covered lagoon/tank or
‘batch-flow’ when feed-stock is produced intermittently.
The resulting gas is of a high energy value, comparable with natural gas, but
has to be cleaned from unwanted elements before using it in a internal
combustion engine.
The efficiency of a particular system depends largely on the conditions under
which the process takes place. Thermophilic digestion will yield higher gas
rates than mesosphilic digestion but need an additional heat source.
In all, the process is complicated and needs knowledgeable personnel in order
to maximize yield and avoid break-down.
The residue, non-volatile solids, are usually sold as fertilizer.
8. 88
Solar Energy
• Solar energy, both heat and electricity is an option to accommodate
power/cooling/lighting demand.
• Photovoltaic options are as yet not feasible for power applications, however,
lighting and small appliances can be served.
• Indirect channeling of solar irradiation can be utilized for factory lighting.
• Solar energy is intermittent, therefore back-up power must be available or the
‘solar-field’ must be of such size and yield that all possible circumstances are
accounted for.
• Indonesia is located in a tropical region, but this does not mean that the sun
is always “on”. Climate issues play a significant role, but cannot always be
predicted. I.e El Nino and La Nina phenomena and even volcanic activity.
• Some solar panels work well in diffuse light, others not at all.
• Solar Panels come in a great variety, one should carefully analyze what
applications can be powered.
• High temperatures > lower efficiency > need for advanced equipment.
• Storage (TES) is a key-element in successful implementation of a solar
option. (Thermal Energy Storage)
9. How much energy is available?
9
In order to establish how much energy can sensibly be captured we need to
know what amount of solar irradiation/insolation actually reaches the earth
surface. This can be established in two ways:
•Empirically – By installing pyrano-metering devices at the desired location and
measuring insolation levels for a period of at least a year.
•By making use of satellite data that is collected since the late 80’s and
provides us with a rich data set (20+ years) of direct insolation and other
climate related information.
It is preferred to make use of the satellite data, although the area’s measured
are rather large; between geographic degrees these area’s measure 1° x 1° or
110 x 110 km. However, for the purpose of calculation the average insolation
values, this method is sufficiently accurate.
For example; in the next slide, the data that is collected for a specific area,
namely 7 degrees South and 112 degrees East. The area South-East of
Surabaya.
10. Actual Data
10
Insolation data valid for Latitude; 7S and Longitude; 112E (MultiBintang)
Major values in terms of thermal energy are in kWh per square meter per day.
Obviously a day means the time that the Sun is apparent above the horizon.
Direct – Diffuse etc. shall indicate:
•Direct – Unobstructed insolation.
•Diffuse – Obstructed insolation. I.e, Clouds, Dust etc. UV and IR spectra will be
captured as well as reflective irradiation.
•Global – The sum of above, safe for ‘assumed’ thresholds, beneath which
capture is not sensible. (This depends largely on the type of absorber installed)
•Clear – Days per month that no obstruction is apparent.
•No Sun – Days per month that no sun is apparent. (Total cloudy days)
•Dir+Dif – The sum of direct and diffuse, without thresholds.
Lat Lon Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann/av a/kWh
Direct Insolation kWh/m2/d -7 112 3.53 3.62 4.58 5.19 5.99 6.10 6.90 7.33 7.36 6.36 4.97 3.83 5.48 2,000
Diffuse Insulation kWh/m2/d -7 112 2.30 2.36 2.24 1.94 1.59 1.46 1.36 1.44 1.65 2.00 2.20 2.25 1.90 694
Global Insolation kWh/m2/d -7 112 4.71 4.89 5.47 5.46 5.42 5.21 5.68 6.31 6.80 6.48 5.62 4.85 5.58 2,037
22Yr Clear d/m -7 112 7.44 7.53 7.40 6.99 6.33 5.97 6.16 6.68 7.25 7.44 7.43 7.43 7.00
22Yr No Sun d/m -7 112 6.11 5.08 5.14 4.60 3.89 3.89 3.67 2.60 3.27 3.73 6.19 8.57 4.73
Dir+Dif kWh/m2/d -7 112 5.83 5.98 6.82 7.13 7.58 7.56 8.26 8.77 9.01 8.36 7.17 6.08 7.38 2,694
11. How to interpret the Data
11
The data presented in the previous slide is ‘gross’ energy, in other words, that
what reaches the earth surface and is collectable.
It is prudent to use the ‘global’ data-set before is known which type of collector
will be used. With this data we can calculate the ‘net’ energy which can be
sensibly utilized. (In the form of hot water or steam.)
During calculation of efficiency of a particular device, the lower threshold can be
determined and insolation yields adjusted accordingly.
In order to arrive at useful figures, we need to find the efficiencies of various
devices that are intended to convert solar energy into hot water and steam.
On the next slide we present some options. From least efficient to most
efficient.
Note that we do not consider domestic sun boilers, since these are usually less
efficient for industrial purposes.
12. 1212
Solar Capturing Devices
• Advanced flat plate collectors (AFPC)
– Temperatures up to 130 °C.
– Medium efficient. (Direct and Diffuse)
– Can drive single effect chillers.
• Evacuated tube collectors. (EHTC) and (EDFC)
– Temperature up to 90 - 170 °C.
– Less efficient on higher temperatures. (Direct and Diffuse)
– Can drive purpose build single and dual effect chillers.
• Concentrating devices. (CPC and HPC)
– Temperatures; 120-170 °C and >250 °C.
– High efficiency. (Only direct for CPC)
– Can drive dual effect chillers (Hot Water and Steam).
13. 1313
Advanced Flat Plate Collectors
• High efficiency on lower
temperatures.
• Also used for cooling
applications.
• Can be used as roof-
coverage, very good
insulation effect.
• Orientation is important.
• Captures both direct as well
as diffuse irradiation.
• Relative expensive,
expected 220-250 €/m2
14. 1414
Evacuated Tube Collectors
• Many different manufacturers available.
(Mostly China)
• Proven design.
• Both in ‘heat-pipe’ as in ‘direct-flow’
configuration. I.e, Evacuated Heat Pipe
Collectors and Evacuated Direct Flow
Collectors.
• Higher diameter tubes are more
efficient. (100mm)
• Orientation is important.
• Captures both direct as well as diffuse
irradiation.
• Reasonable price, 150-200 $/m2
15. 1515
Concentrating Devices
• Both parabolic troughs as well as
evacuated heat pipes.
• Sun-Tracking is required.
• High efficiency for both.
• Parabolic Trough Collectors need
‘direct’ irradiation contrary to the
heat-pipe variant.
• Temperatures:
– PTC 170 °C – 250 °C
– HPC 120-170 °C
• Prices:
– PTC 150 – 200 €/m2
– HPC 120 – 150 €/m2
• HPC (concentrating) – also named CHPC
• PTC - also named CPC ‘concentrating parabolic collector’
16. 1616
Efficiencies of Solar Devices
1. In order to calculate efficiencies of collector devices, we need important
information regarding internal heat losses under various circumstances.
Further data regarding average ambient temperatures as they influence
efficiency as well. This data is for most collectors available with certification
institutes, while ambient data can be retrieved from meteorological
institutes.
2. It has to be determined, what level of heat must be captured in relation to
usage. F.I, Hot Water at a certain temperature, or steam at a certain
pressure. Thermal oil can be used as well, normally this method serves
higher temperature applications like spray dryers etc.
3. The amount of energy (per shift or per hour in kWh) needs to be
determined. An example is shown on the next slide.
4. As operations extend after sun-hours, Thermal Energy Storage (TES) must
be considered. F.i, Hot water storage, cold water storage and steam
accumulators.
17. 1717
Efficiencies of Solar Devices
This example concerns superheated water at a
pressure of 8 Bar(a). The efficiency at G=900
W/m2 is 61%. Naturally, the insolation varies
with sun-position at a certain time of day,
therefore when plotted in a graph, we can
calculate an average efficiency of 47% over the
entire day. With an daily insolation of 5,600
W/m2, total collected energy will be 2.656 kWh
per square meter aperture per day.
If applied to office cooling, a field of 2000 m2
would generate 2,264 RT per day.
This can be utilized during 8 office hours, or
longer if appropriate storage is installed.
Next slide will explain that higher efficiencies
and lower usage temperatures have an impact
on total efficiency.
Steam Process (Superheated water)
Maker XX
Type U tube - 2-16 (100mm) Example 2-stage abs. cooling
Gross area 4.2 m2 M2 2000 5,307 kWhd
Aperture area 2.9 m2 Panels 482
Absorber area 2.8 m2 COP 1.5
Min Flow Rate l/h kWc/d 10,404
Max Flow Rate l/h RT/d 2,264
Nominal Flow Rate 457 l/h
Calculation of Gross performance excludes heat losses in piping & vessels
1 Conversion factor η0 0.841 from testreport
2 Loss coefficient a1 1.047 W/(m2K) from testreport
3 Loss coefficient a2 0.010 W/(m2K) from testreport
4 Daily Insolation Gd 5580 W/m2/d from tabel
5 insolation level G 900 W/m2 calculation
6 Ambient T TA 30 °C input
7 Average Manifold T TM 130 °C calculation (Ti+To)/2
8 Manifold in T Ti 90 °C input
9 Manifold out T To 170 °C input
10 X value X 0.111 calculation (TM-TA)/G
11 Aperture area m2 2.93 from testreport
12 Calculation η(x) = η0 - (a1*X) - (a2*G*X2
)
13 efficiency η(x) % 61%
14 yield vs G W/m2 550.2
15 yield panel vs G W 1612.0
18. 1818
Efficiencies of Solar Devices
This example concerns heated water at normal
pressure. The efficiency at G=900 W/m2 is 76%.
Naturally, the insolation varies with sun-position
at a certain time of day, therefore when plotted
in a graph, we can calculate an average
efficiency of 70% over the entire day. With an
daily insolation of 5,600 W/m2, total collected
energy will be 3.944 kWh per square meter
aperture per day.
If applied to office cooling, a field of 2000 m2
would generate 1,683 RT per day.
This is importantly lower than the first example.
The reason is that the application (absorption
chilling in single stage) is less efficient
compared with the previous example. In this
case it would be prudent to utilize the energy for
other purposes.
Hot Water Process
Maker XX
Type U tube - 2-16 (100mm) Example 1 stage abs. cooling
Gross area 4.2 m2 M2 2000 7,889 kWhd
Aperture area 2.9 m2 Panels 482
Absorber area 2.8 m2 COP 0.75
Min Flow Rate l/h kWc/d 5,917
Max Flow Rate l/h RT/d 1,683
Nominal Flow Rate 457 l/h
Calculation of Gross performance excludes heat losses in piping & vessels
1 Conversion factor η0 0.841 from testreport
2 Loss coefficient a1 1.047 W/(m2K) from testreport
3 Loss coefficient a2 0.010 W/(m2K) from testreport
4 Daily Insolation Gd 5580 W/m2/d from tabel
5 insolation level G 900 W/m2 calculation
6 Ambient T TA 32 °C input
7 Average Manifold T TM 78 °C calculation (Ti+To)/2
8 Manifold in T Ti 60 °C input
9 Manifold out T To 95 °C input
10 X value X 0.051 calculation (TM-TA)/G
11 Aperture area m2 2.93 from testreport
12 Calculation η(x) = η0 - (a1*X) - (a2*G*X2
)
13 efficiency η(x) % 76%
14 yield vs G W/m2 688.1
15 yield panel vs G W 2016.2
19. 1919
How to Proceed?
The previous slides show that the choice of collectors and size of the
field highly depends on the following considerations:
•Efficiency of the collectors. (Initial yield, internal heat losses)
•The end temperature of the medium heated; usually (superheated) water but thermal oil
is possible.
•The temperature variance, meaning the heat dissipated to equipment or product in a
certain unit of time. (heat-flow)
•Reliability of operations, in terms of available back-up.
•The duration in which the collected energy is used. (one shift operations or more, in
which a TES must be provided)
•Coverage:
– Auxiliary source of energy. “Take what you can get”
– Main coverage, based on a certain size. Top-up with conventional sources.
– Total coverage. Includes ‘oversized’ solar field and large or eutectic TES.
•Cost and ROI.
•Possible emission reduction.
20. Investment & ROI
20
Capex, Opex and ROI are important drivers in this energy sector, many projects
end-up on the shelf because these figures are difficult to obtain or remain shady
due to misinterpretation and or misunderstanding. However, if one would be
able to factor-in all the available data, one could ‘paint a picture’ that is more
appropriate for a decision making process.
This requires in-depth analysis of the entire concept that must include;
Current an future demand and cost to generate. In order to calculate Capex, returns and pay-back time.
Options for energy replacement. In order to establish the most suitable solutions in
respect to expected developments.
Lowest recorded insolation levels
Months with low recorded insolation.
Number of ‘No-Sun’ days per year.
In order to establish the most appropriate seizing for
the ‘solar field’. Also in relation to investment cost and
returns.
Highest insolation incidents. Both momentarily
and over time.
In order to establish seize and type of TES.
(Accumulators, conventional TES and Eutectic TES.)
