Johnathon Wheaton October 23, 2014 Multi-disciplinary Senior Design I P15484 – Solar Assisted Essential Oil Distiller Propane Burner and Photovoltaic Back-up Sub-Systems Introduction The solar assisted essential oil distiller will boil water using solar power supplemented by a gas burner during night time or when weather conditions are adverse. The team has chosen a solar trough design to collect solar energy to boil water. Because this design is difficult to model, complex to design and build, prone to damage, and less proven by industry, the team has chosen to continue with a photovoltaic method of boiling water as a back-up plan in the event that the solar trough does not meet the project engineering requirements. Engineering requirements will be developed for each critical sub-system of the distiller. These requirements will constrain and guide the design of components. Each engineering requirement at the sub-system level will likely be related to the system level engineering requirements but with more specificity. In order to meet the engineering requirements S6 and S7 (recover oil at a rate comparable to known industry values, recover oil at a yield comparable to known industry values) water must be boiled at a sufficient rate. The gas burner sub-system and photovoltaic back-up sub-system both must produce steam at this rate while still meeting all other engineering requirements. A steam rate that is too low would result in long cycle times and poor extraction rates. An excessively high steam rate would require a substantially larger or more complex condenser and could overheat the plant material, producing a low quality of oil. The cost saving to make vs buy gas burner and photovoltaic components is likely very little or negative because of the relatively low cost of currently available products and/or the specialty tooling required. The team will be pursuing off-the-shelf products for most if not all gas burner and photovoltaic components and allocating team efforts towards the design of more complex and unproven sub- systems. For this reason, specifications for the sub-systems will be related to the specification of benchmarked products. The gas burner sub-system will operate by feeding a combustible gas underneath the water where it will be burned. The photovoltaic sub-system will collect energy from the sun and convert it to electricity. This electricity will then be sent to a battery controlled by a charge controller and sent to a resistor heating element located in or under the water. Figure 1 Gas burner sub-system illustration.
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Johnathon Wheaton October 23, 2014 Multi-disciplinary Senior Design I P15484 – Solar Assisted Essential Oil Distiller
Propane Burner and Photovoltaic Back-up Sub-Systems
Introduction The solar assisted essential oil distiller will boil water using solar power supplemented by a gas burner during night time or when weather conditions are adverse. The team has chosen a solar trough design to collect solar energy to boil water. Because this design is difficult to model, complex to design and build, prone to damage, and less proven by industry, the team has chosen to continue with a photovoltaic method of boiling water as a back-up plan in the event that the solar trough does not meet the project engineering requirements. Engineering requirements will be developed for each critical sub-system of the distiller. These requirements will constrain and guide the design of components. Each engineering requirement at the sub-system level will likely be related to the system level engineering requirements but with more specificity. In order to meet the engineering requirements S6 and S7 (recover oil at a rate comparable to known industry values, recover oil at a yield comparable to known industry values) water must be boiled at a sufficient rate. The gas burner sub-system and photovoltaic back-up sub-system both must produce steam at this rate while still meeting all other engineering requirements. A steam rate that is too low would result in long cycle times and poor extraction rates. An excessively high steam rate would require a substantially larger or more complex condenser and could overheat the plant material, producing a low quality of oil.
The cost saving to make vs buy gas burner and photovoltaic components is likely very little or negative because of the relatively low cost of currently available products and/or the specialty tooling required. The team will be pursuing off-the-shelf products for most if not all gas burner and photovoltaic components and allocating team efforts towards the design of more complex and unproven sub-systems. For this reason, specifications for the sub-systems will be related to the specification of benchmarked products.
The gas burner sub-system will operate by feeding a combustible gas underneath the water where it will be burned. The photovoltaic sub-system will collect energy from the sun and convert it to electricity. This electricity will then be sent to a battery controlled by a charge controller and sent to a resistor heating element located in or under the water.
Figure 1 Gas burner sub-system illustration.
Figure 2 Photovoltaic sub-system illustration.
Objective The purpose of this paper is to identify the energy specifications for photovoltaic and gas burner sub-systems. Method In order to understand the energy requirements of the photovoltaic and gas burner sub-systems, the rate of steam production must be identified. Vetiver root distillation requires 2 Kg of water to be boiled each hour for each pound of plant material being processed (Dewi et al, 2012, Tutuarima, 2012 ). Customer requirement CR6 specifies that the distiller will be processing at least one pound of plant material.
1 𝑔𝑎𝑙𝑙𝑜𝑛 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 = 3.7854 𝐾𝑔 → 0.2641 𝑔𝑎𝑙𝑙𝑜𝑛𝑠 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 = 1 𝐾𝑔 The rate of water boiling was calculated to be:
0.45 𝐾𝑔ℎ𝑜𝑢𝑟
3.7854𝐾𝑔𝑔𝑎𝑙
= 0.1189𝑔𝑎𝑙
ℎ𝑜𝑢𝑟
A 25% design margin is being applied to critical measurements in the distiller:
25% 𝑑𝑒𝑠𝑖𝑔𝑛 𝑚𝑎𝑟𝑔𝑖𝑛 → 0.1486𝑔𝑎𝑙
ℎ𝑜𝑢𝑟
0.1486 gallons of water should be boiled each hour in order to properly extract oil. Gas Burner Gas burners on the market are most often sold with BTU specifications. In order to identify the number of BTU’s required to boil 0.1486 gallons of water it must first be converted to weight in pounds:
This energy requirement is also dependent on the change in temperature:
∆𝑇 = 212°𝐹 − 65°𝐹 = 147°𝐹
The BTU’s required to boil 0.1486 gallons of water in one hour is found to be:
𝑤Δ𝑇 + 𝑚𝐻𝑣 = 𝐵𝑇𝑈′𝑠
1.238𝑙𝑏(147℉ + 973.63𝐵𝑇𝑈
𝑙𝑏) = 1,387𝐵𝑇𝑈
And even more power is required to account for efficiency:
With 20% efficiency (“Cooking…”, 2012)
1,387BTU/0.2 = 6,935 BTU
Photovoltaic
Photovoltaic panels on the market are most often sold with power specifications in Watts. During the system level design phase of the project the energy required to boil 2 gallons of water was found to be 19.3MJ, or 1.43 MJ for 0.1486 gallons of water. This energy, required each hour, results in a 397 Watt requirement before efficiency loss. The following efficiency losses are assumed:
Accounting for these inefficiencies, the solar panel must be able to produce 496 Watts.
397𝑊
0.85
0.94= 496𝑊
Results It was found that the gas burning sub-system must produce and withstand a minimum of 5,459 BTU’s. The photovoltaic panel must produce a minimum of 621W with the sub-system components able to withstand this power. Discussion These power requirements have been added to the engineering requirements flow-down (PM11 and PV12). These values are minimum requirements that must be met to achieve the steam rate recommended by Tutuarima and Dewi. The essential oil distiller should have a capacity to provide more power than these specifications to account for unconsidered factors like convection and product wear. A 25% design margin is being used on critical measurements of the distiller such as these power requirements.
Budget permitting, the final design should incorporate control systems to adjust the power outputs of the gas burning and photovoltaic systems. This would ensure much higher control over steam rate and thus produce a higher quality of oil. Low cost benchmarked products for controlling gas burning are limited to control valves which are operated manually. Photovoltaic water heating systems often use a thermostat to control the power to the heating element at a relatively low cost.
The photovoltaic sub-system is substantially out of the team’s budget of $800. Benchmarking indicates the cost of a photovoltaic system will cost at least $1,026.72 (see sub-system collaborative document). The burner system, however, holds a cost of less that $100.
What is the minimum (or recommended) thread engagement necessary to prevent leaks?
According to CNCexpo a thread length of 1.5 times the diameter of the fastener is a good rule of thumb (http://www.cncexpo.com/ThreadEngagement.aspx).
Information other sub-system owners:
How deep will the water be?
What material is the boiling chamber made of? Stainless steel.
Will the chamber have a wall thickness or dimensions that will allow for a 1” NPT hole to be tapped with enough thread engagement to prevent leaks?
No – we need to look into modifications. Contact John Bonzo.
What volume of water will be present in the chamber? 2.16 gallons per process minimum
What is the diameter of the chamber? Benchmarking shows 10-14 inches.
Concept Selection Concept 1:
An external heating element is much less efficient than a submersible heating element and is not substantially cheaper than other heating elements. Concept 2: If the heating element is 0.25” in diameter (smaller than any benchmarked products) then the thread length must be 0.375” (1.5 times diameter rule of thumb). No reasonably priced vessel will have a wall thickness of 0.375”.
The wall of the vessel could be modified to provide this thickness but that would require welding and extended design time (high project risk). Instead, the male NPT threads on the heating element could be used to seal and fasten the element to the wall of the vessel.
Photovoltaic panel:
Photovoltaic panels on the market are most often sold with power specifications in Watts. During the system level design phase of the project the energy required to boil 2 gallons of water was found to be 19.3MJ, or 1.43 MJ for 0.1486 gallons of water. This energy, required each hour, results in a 397 Watt requirement before efficiency loss. The following efficiency losses are assumed:
Accounting for these inefficiencies, the solar panel must be able to produce 496 Watts.
397𝑊
0.85
0.94= 496𝑊
All benchmarked photovoltaic panels were considered. Dividing the panel cost by Watts produced helped select the lowest cost option. $50 was added to the cost of panels not included in kits to account for additional wiring and fittings that will be required. The Dasol DS-A18-60, 60W 12VDC solar panel meets all sub-system engineering requirements at the lowest cost per Watt of all benchmarked panels. Four of these panels will be needed to produce the minimum power supply. Battery:
A battery will be used to maintain power to the heating element during cloud cover. The team has chosen to design the sub-system to provide power for 15 minutes of cloud cover. This requires (as specified in the sub-system requirements flow-down) a battery that can provide at least 125 Wh (Wh are a standard industry measure for batteries). Charge controllers (discussed below) typically require the same voltage for both the photovoltaic panel and battery. Because a 12V panel has been selected meaning the battery must also be 12V. The 12V, 12Ah benchmarked battery is selected because it matches the voltage of the photovoltaic panel and exceeds the necessary power storage.
Charge Controller
A charge controller protects the photovoltaic system from overcharging the battery to prolong the life of the battery. The input and output voltages and amps must be specified to select a charge controller. Module Short Circuit Current x Modules in parallel x Safety Factor = Array Short Circuit Current* 7.5A x 4 x 1.25 = 37.5A (minimum controller input current)
Total DC Connected Watts / DC System Voltage = Max. DC Load Current* 500 W / 12 V = 42 Amp (minimum controller output current) The Morningstar Tristar TS-45 is selected because it matches these specifications. *http://www.civicsolar.com/resource/how-size-charge-controller
Works Cited "Charging and Discharging Lead Acid Batteries." Charging and Discharging Lead Acid Batteries.
N.p., 2014. Web. 23 Oct. 2014. "Cooking with Propane." Alliant Gas. N.p., 2012. Web. 23 Oct. 2014. Dewi, P., S. Berutu, R. Rahardianto, and H. Abdurrachim. "STUDY OF THE UTILIZATION OF
FLUID FROM A CONDENSATE POT FOR ESSENTIAL OIL EXTRACTION." Diss. Bandung Institute of Technology, 2012. New Zealand Geothermal Workshop (2012): n. pag. Print.
"Solar Charge Controller Basics." Northern Arizona Wind & Sun. N.p., 2014. Web. 23 Oct. 2014. Tutuarima, Tuti. "Process Design of Vetiver Oil Distillation by Increased Pressure and Gradual
Steam Flow Rate." Diss. Bogor Agricultural U, 2012. N.p., 18 July 2012. Web. 26 Oct. 2014. <http://fateta.ipb.ac.id/~tin/images/stories/jurnal/TESIS,%20POSTER%20PENELITIAN/Tuti%20Tutuarima%20F351060031/Abstract.pdf>.