StevenGrootaert

renewable energy collection package 

A package is defined by two containers stacked in a well car or what will fit onto two semi trucks. One of the containers will contain a deployable solar array and the other will contain vertical wind turbines to create an on-site wind farm. Outpost Solar is a company that manufacturers deployable solar panels for military applications and four of them can be stacked in the space of one standard shipping container. The vertical axis wind turbines can be disassembled and stored within the container and be deployed by fitting them on top of the container to take advantage of the wind coming from any direction, even at low speeds. After an analysis of manufacturer information and National Renewable Energy Laboratories, the expected energy production potential for the entire package is 253.5 kWh on an average day.

map / product image credit (left to right) NREL: http://www.nrel.gov/gis/solar.html, Outpost Solar:  http://outpostsolar.com, Windspire: http://www.windspireenergy.com

on-site hydrogen production

For this investigation hydrogen production is used as a means of energy storage as opposed to storing energy in dry cell batteries. Dry cell batteries used at this scale are not sustainable due to the amount of resources and energy used to create them. Additionally, energy stored in hydrogen will not degrade over time and if the energy used to produce the hydrogen via electrolysis is generated with renewable energy the entire process is emission free.

flow of water and energy

This diagram describes the water and waste cycle of the MERS program in relation to energy used for heating and treating water. In order to manage the waste on-site a MuckBuster 400 is being used to digest the waste. However, the energy gained from the reaction is minimal in comparison to the energy demands of the MERS program.

The space required for solar thermal water heating may out weight the practicality for the amount of water needed for the number of people using hot water. However, it may be enough to raise the water temperature to increase the efficiency  of the tank-less water heaters. The water being treated could be stored post treatment in a way to take advantage of solar gains.

summary of on-site MERS water use

While the water consumption profile of the MERS program is large, the ability to filter and treat gray water allows much of that water to stay in a closed loop cycle. The largest use of water is by 100 people showering on a daily basis. If the crew were to shower every other day than logically that amount of water would be cut in half and result in a drastic water savings. However, saving this water does not impact the amount of water needed to be brought on-site if it is treated.

Accounting for nearly a third of the water budget, the largest source of water leaving the loop is black water from toilet flushing. If chemical toilets were to be used, than one tanker truck of water would last the MERS detachment for four months.

power load based on program

In order to determine the size of a renewable energy array, or the amount of hydrogen needed, the amount of power consumed by the MERS detachment needed to be established as a baseline. When attempting to assess the actual power load of the MERS detachment, many assumptions were made to manage the variables. The Emergency Operations Vehicle (EOV) is a large office trailer filled with specialized equipment that has two 40 kW generators, it is assumed that one of those generators is redundant. It is also assumed that the 40 kW generator is sized such that it is not running at full capacity at all times.

In the current model each individual program within the MERS detachment has it’s own generator and a back up. Since power can not be transferred between programs it is assumed that each generator is oversized to ensure power is always available during peak loads. If the generator was micro-centralized, power could distributed to each program and be sized such that even if each program was drawing it’s designed maximum load of 75% the generator is still running at peak efficiency.

diesel fuel use estimations for speculated loads

Determining the amount of diesel fuel used by the MERS detachment is important for the comparison between diesel fuel and hydrogen as a fuel source. It would also serve as a means to quantify the amount of fuel savings between various options. Alternatively, the actual kWh of electricity used by the MERS detachment could be quantified if information were to be made available regarding the amount of diesel fuel used during the deployment.

Calculating diesel fuel consumption is purely an estimation as each diesel generator is unique. However a generalized equation can be used based on the rated output of the generator. It is notable that although a generator of larger size, such as these, will operate most efficiently the nearer it is to its peak output capacity, however the equation is considered accurate between the range of 75%-100% of capacity due to its generalized nature.

estimated power use over 24 hours by load type

Establishing a power load curve profile and power schedule for corresponding renewable energy production over the course of a 24 hour period would yield a more refined estimate of the amount of energy needed by the MERS detachment.

For the more energy intensive programs categorized as 40 kW programs, the load estimation was assumed to be greatest during the daylight hours. The red line is an indication of the average value between these three programs. During peak hours the average value is 30 kW/h, and over the course of 24 hours the value is 1900 kWh.

The personnel driven programs vary with behavior such as nightly routines and shift changes. The red line is an indication of the additive value of all the energy over a 24 hour period and results in approximately 540 kWh.

compared to renewable energy potential

Combining the average value for the larger programs and the additive value for the smaller programs results in an overview of all the estimated energy used by the MERS detachment. The average of 2150 kWh a day is the result of peaks of high energy use and valleys of lower energy use in the late night hours and early morning hours. In terms of renewable energy production this daytime peak generally coincides with the arrays ability to provide energy during the day, but falls short in the overnight hours.

electric load and resulting hydrogen consumption 

There is a direct correlation between electrical load and hydrogen consumption. The resulting table reviews the amount of hydrogen that would need to either be brought on-site or generated in order to satisfy the energy load. Hydrogen production is approximately 60% efficient and as a result, more electricity would be needed in order to produce enough hydrogen to meet that load.

summary of various power options

Considering the initial goal of MERS is to be resource independent for 30 days, establishing a nearly indefinite self-sustaining system would be superfluous. Then a primary concern for the MERS unit would be the amount of space and equipment required to provide life support services. When using diesel, a variation of the micro-centralized system offers the greatest utility for MERS, where one tanker truck can provide nearly all the energy required for a 30 day deployment and no other equipment is needed for operation.

When using hydrogen as a fuel source, it would be best for the MERS unit to use hydrogen produced with renewable energy off-site and brought on-site via containers. A MERS detachment would require 4 containers of hydrogen for approximately 30 days of power due to the inability to feasibly compress hydrogen gas into a liquid for transit. One kilogram of hydrogen at room temperature would fill a 40 foot container.

space requirements of self-sustaining energy

To grasp the single largest issue with an outfit such as MERS utilizing a renewable energy array for self sustaining on-site hydrogen production this diagram illustrates the amount of space required. What is clear is that allocating this much open space for energy production and storage would not be feasible for the MERS detachment simply due to the scale of energy needed by the program.

summary of various power options

When utilizing the renewable energy array the energy can either be used directly by the MERS program and reduce diesel consumption, or it can be used to produce hydrogen to be used during overnight hours. In essence energy storage is critical, if the amount of energy being collected is not being stored it would be impossible to satisfy the energy demand of MERS due to the power draw that occurs when the array is unable to collect energy.

The variables determining the duration of stay include the size of the renewable energy array, the amount of fuel brought on-site, and if the array is contributing to the production of hydrogen or peak load reduction.