Design Issues
Jake Mazur
Eric Tarkleson
Josh Wong
Ben Kershner
November 19th, 2008
Team 2 – Design Issues
The task of this team was to design a solar powered multi-seat computer system for
deployment into rural schools. This included researching what technologies are
currently available to provide the most efficient and cost effective method of
running multiple computer terminals from a solar system. This task itself is a
serious engineering challenge and it turns out that sourcing components for such a
system in under-developed areas is also a big challenge.
Certain considerations must be taken when designing anything that is going
to be deployed to a foreign country, especially a developing one. When the rural
element and placement inside of a classroom are added to the equation it only
compounds the already existing issues.
Product Safety
Since we are designing a system that will be deployed in a school with no
preexisting power, and around people without much experience with electrical
equipment we need to take some extra precautions to make sure that the entire
system is as safe as possible. There will be solar panels that will either be mounted
on poles outside of the building or on the roof so we will have to make sure to
protect these cables because they will carry high currents. The battery bank also
needs extra safety measures because it will have the potential to unleash huge
amounts of current should a short, or other low resistance connection (i.e. body)
cross the terminals.
The solar panels will be mounted outside. If we mount them on the roof then
we need to make sure that the cable runs go into the structure through a watertight
seal. Also there will need to be an earth ground installed in case lightning hits the
building. The building itself must be structurally sound enough not only for the solar
panels but also for several people so that installation and maintenance is safe.
If the building is orientated in such a way that the panels can not face the sun
while they are on the roof then they will have to be mounted on a pole outside of the
school building. In this case extra precaution must be used to insure that a person is
unable to access any wire leads because the current can easily kill a person. Also the
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Team 2 – Design Issues
cabling will have to be run underground so the wires will have to be enclosed in the
proper type of duct to that they cannot be cut by someone digging in the area. They
also must be completely weatherproof to avoid the wire insulation breaking down
from the elements. One advantage to this setup is that the structure that the panels
hang on can be used as an earth ground for the entire system.
Once inside the building all wiring outside of the case should be in ductwork.
This prevents a person from easily cutting the wires and also prevents animals from
chewing through the insulation. The system case must have a hole that is not sharp
so that the wires cannot fray over time. Also cabling should be secured to the case so
that it cannot easily be pulled out which could cause short circuits or broken
hardware. Any short unintentional short circuits have a large probability of
destroying the expensive equipment nearby or causing a fire.
The battery bank must be carefully installed so as to minimize any possibility
of short circuits. Each battery terminal should have a cover installed so that it is
difficult to touch the electrodes accidently. All batteries should also be secured to
the casing so that they cannot move if the whole case is tipped or moved.
There must be circuit breakers at several key points in the system to insure
that if there is a problem the system will cut off power to itself and hopefully save
the equipment from being ruined. There will be a circuit breaker between the solar
panel array and the Charge Controller and also between the Battery Bank and the
Inverter. These will trip if current exceeds expected ratings and will also allow the
system to be manually shut down if the need arises.
Following these simple precautions should allow the system to be safe from
prying fingers, weather, animals and equipment failure. Also in the case of a failure
troubleshooting should be easy because if our battery management system is
running it will provide feedback about which components are not working. If a
breaker is reset then it will also provide clues as to which part of the system failed.
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Team 2 – Design Issues
Product Lifecycle Management
The solar powered computer system is designed to be easily assembled,
maintained, and recycled. The majority of the components used are commercial off
the shelf components. This allows for easy replacement of damaged components
and allows using other compatible components with minimal effort. It also allows
for the efficient upgrading of obsolete components without requiring a redesign of
the entire system.
The system is comprised of four major independent systems, the server, the
satellite dish, the solar array, and the battery array. Each of these major systems can
be replaced by a compatible solution without the replacing or modifying any of the
other components. There is one crucial component that is unique to our system, the
power monitoring hardware. This hardware and software are custom built, but it
interfaces with the server using a simple USB connection, and it is compatible with
all UNIX-based operating systems.
One of the greatest strengths of the design is the multi-terminal approach
taken. Many hardware based multi-terminal approaches exist, but these add many
more points of failure. The approach taken here is software based. This allows any
server fitting a generic set of specifications to be used. Because of the constantly
changing nature of computers, this is a powerful tool in reducing cost as no special
hardware like thin clients are needed. Also software does not become obsolete as
quickly as hardware and can be easily updated if needed.
It is anticipated that the system will be completely sourced by Lenovo and
then shipped as a single unit to the target deployment areas. Based on experiences
dealing with foreign suppliers, it makes sense to have the units made in the US and
then shipped to the developing countries. This allows for the highest quality
components at the lowest possible cost. Because the primary components are
already made, there is no need to take into account most of the production issues
other products face. The custom hardware for monitoring power can easily be made
using the same facilities that manufacture computers components.
As far as distribution of the whole system, there are many options. Because
the system is modular, each piece can be shipped individually to the area, or the
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Team 2 – Design Issues
entire system can be shipped at once. The modularity also allows for replacement
components to be shipped. The anticipated deployment for a single system is in
excess of five years. Over this time various components will reach the end of their
specified lifecycles (e.g. the battery array) or even fail completely due to weathering
(e.g. the solar panels). These can be fixed easily by drop-in replacements.
Because the system is connected to the Internet, it is possible to modify the
software at any time. In addition to correcting bugs that are discovered after the
system has been deployed, this can also be used to back up user data to more secure
data centers. It is also possible to fix many of the problems that the users can
encounter remotely.
To improve the performance and cost of the next generation of the product,
the power monitor hardware is set to gather more data then needed for the typical
operation of the system. This additional data will provide insight into usage pattern,
actual power consumption versus theoretical power consumption and other
important data. This data will help in determining how many solar panels or
batteries need to be added or removed. Additional logging of other statistics, such as
processor usage in the server and memory usage will allow a more efficient server
to be designed.
Rapidly Sourcing Components Internationally
Getting all of the necessary parts in place stateside is one issue. Custom
building the computer system took about a week by the manufacturer and then
shipment took most of another working week. Upon arrival of the computer more
delays where experienced as the unexpected happened, the motherboard was
defective. Such delays cannot be accounted for in the planning stages but must be
dealt with anyway. There will always be an unexpected delay.
Doing so on another continent is completely different. Sourcing the same
computer system in an under-developed area obviously takes even longer as the
distribution channels are not there. A company that has a huge presence in North
America may only have one employee covering even such a large area as the entire
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Team 2 – Design Issues
African continent. This one employee may have to get in touch with other vendors
and distribution channels to make shipment to a remote rural location possible.
Anytime more people are involved in the chain there are more delays. Also, when
communicating across continents it is often only possible to have one information
transaction per day, as there is a large time-zone difference.
Remotely finding and contacting a supplier in areas where Internet access is
limited is quite difficult. Due to time-zone differences, language barriers and longdistance calling charges the phone is not as useful as one might think. Finding the
right supplier is closely tied to the geographical location of deployment areas and
transportation of the equipment is an issue. Photovoltaic panels are fragile. The
panels need to be handled with utmost care anytime they are moved as a single
crack in one cell can render the efficiency of the whole panel useless. This is
especially a challenge in rural areas due to the condition of the roads. Just one of the
batteries weighs 130 pounds, which is another transportation challenge. Ultimately
your system components are limited to what is available in the deployment area.
Such a design should begin from the opposite end. Not what optimum components
you want to put in the system, but what are the most optimum components from
what is available.
While the team had a good idea of an optimum system setup relatively
quickly, sourcing components while working in a short time frame for distribution
in a rural area proved to be a real challenge.
Environmental Issues
Though most of the components are not inherently toxic, complications could
arise given the specific implementation. Though it has not been the practice of this
team to include wet-acid type batteries in the design, certain situations could arise
where the use of such batteries is unavoidable.
Wet-acid type batteries pose a three prong environmental threat. In their
transportation, they are marked as a chemical hazard, and as such, more care must
be taken when shipping them, raising both the cost and the chance of an incident.
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Team 2 – Design Issues
After installed, aside from the previously listen environmental hazard, they also leak
hydrogen gas, creating a health and safety hazard as well.
Disposing the batteries, and indeed the entire system presents the greatest
challenge. Many of the components used cannot be simply thrown away. Although
very few of the developing countries have laws governing the disposal of digital
waste, it would be irresponsible to deploy these systems without a proper disposal
plan. Because of the materials of the system, the best way to dispose of the system
would have to be drafted on a country-by-country basis. The worst-case scenario
would be to pack everything up and ship it back to the US for disposal, given that
many of the developing countries lack the proper facilities to process digital waste
and it will end up in a landfill.
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