[Editor's Note: This a a portion of a longer article submitted as a letter to the Department of Water and Board of Water Supply. For more on this subject please contact David Ward]
by David Ward on 10 Janaury 2008
The Kauai Department of Water and the Board of Water Supply of the County of Kauai are in the process of implementing a long-range plan of capital improvements called Water Plan 2020. However, I believe that this plan needs to be set aside until an energy audit has been conducted and the energy sustainability of the system can be assured. Contingency plans, instead, need to be formulated so that in the event of a Civil Defense Emergency, A PLAN IS IN PLACE and can be
implemented. Government should plan for the worst, in order to mitigate it. Agencies need to look at the most likely eventualities (as well as the consequences of the worst cases), in order to choose between alternatives. A crucial factor to all this is: the water supply system is dependent on oil-powered electricity to function.
The existing thirteen (13) unconnected and outdated systems pump water from 48 underground wells, UPHILL, to 43 tanks. The pipes leak so much that 25% of the water and energy are lost and un-metered (www.kauaiwater.org). This system evolved during a time when there was abundant water and before the current concern about the future of fossil fuels or global warming.
We are addicted to oil but this is no comparison to our dependency on water. A person can live without food for over a month, but only a few days without water. We need to ask whether our access to water is both sufficient and assured. The answer is NO!
Our power and water utilities are interdependent and energy-hungry. The Department of Water is KIUC’s largest consumer, satisfying its energy needs almost exclusively by burning fossil fuels. Both utilities are unable to withstand interruptions to their energy source for more than a few days at the most. From the KIUC Strategic Plan 2008 – 2023 KIUC is committing itself to generate at least 50% of its electricity renewably without burning fossil fuels within
15 years. However admirable this may be, it is too little too late. The impending peak in the world’s production of oil will have severe consequences to the ability of KIUC to continue to remain in operation. Failure by the Water Department to become energy independent would be devastating.
Source and conveyance
Most of the County’s water supply comes from ground water that requires extensive pumping resulting in the Department of Water being the largest consumer of electricity in the County, representing (?) % of total use. Typically 94% of all energy purchased by a water utility ends up being used to pump water with the remaining 6% covering office and administration uses.
The energy cost for water systems depend heavily on whether energy is consumed during on-peak or off-peak periods. Within system constraints try to take advantage of the price difference by pumping off-peak and generating on-peak. Yes, the Department should be generating power. The number of viable sites for generating pressure reducing valves needs to be closely examined and where cost effective these in-conduit hydropower units should be installed.
Wherever there is flowing water, there exist both energy and the potential to capture and utilize that energy. Pipelines that convey water supplies by gravity have energy that could be captured, but care must be taken to make sure sufficient head, or force, remains to carry the water to its final destination. Whenever pressure-reducing valves are used to reduce the energy in a water or wastewater system, there is an opportunity for energy production.
Water utilities are unique in having the ability to move electrical load by filling storage tanks and using them like batteries when power is expensive. The Department of Water and KIUC should form a synergistic partnership in the development of a pumped storage hydro system. This system would increase the intermittent capacity of the grid and smooth the electricity load curve, reducing the need for expensive diesel peaking generation. The additional storage capacity
would provide additional fire protection and help recapture some of the pumping costs.
Pumped storage hydro systems are comprised of two adjacent reservoirs of water, one at a significantly higher elevation than the other. Water from the lower reservoir is pumped up to the upper reservoir during off peak periods when generation costs are lower and there may be unused non-curtailed generation available. During peak periods or whenever the extra generation is needed, water is released from the upper reservoir and passes through a generator on the way down
to the lower reservoir, producing electricity. Pumped storage hydro systems are fairly efficient, with roughly 70% to 85% of electricity used to pump water regained in generation.
Two or more existing reservoirs or lakes could be connected with new pipeline and penstocks for water pumping and power generation. This type of development could increase operating flexiblility and peaking capacity without the need to construct new reservoirs.
However, the low energy density of pumped storage hydro systems requires either a large body of water or a large elevation gradient to function efficiently. Using only treated water storage tanks makes large elevation gradients a paramount consideration. Pumped storage hydro systems can help regulate system frequency by quickly adjusting generation or curtailment in response to changing electricity demand and supply. These adjustments in output can occur in a matter of
image above: Shore of Kauai's Wailua River - the largest in the state. Photo by Juan Wilson
Water Plant Design for Energy Efficiency
As mentioned above, the first place to look for energy savings in a water system is in the pumps and motors. Even before looking to the actual pumping equipment, however, it is useful to understand how the energy imparted to the water in a pump is expended. The majority of the pumping energy should apply to developing pressure, or head, in the distribution system, in turn delivering the treated water to customers.
Unfortunately, much of the energy to be used in moving water is actually expended in battling friction in the water lines. Such things as pipe size and material and number and location of valves, elbows, tees, reducers and other system components have a great impact on the amount of friction in the system. Most operators or managers, unless in the midst of a system upgrade, have little input on the location of these system components. If the opportunity should arise,
however, an analysis of the overall effect of the type and placement of these components should be conducted.
Another aspect of the water plant design that operators and managers have much more control over is the operating procedures of the plant. To truly maximize the energy savings in the system, it is important to understand such aspects of operation as operating cost, pump performance curves, friction loss sources and motor efficiencies. Even an operating procedure as simple as using a valve to throttle the flow rate of the system can have tremendous impact on the overall
Probably the most important operating consideration is the flow rate of water through the system. This water velocity has direct impact on the amount of friction seen in the water system pipes and components.
Water systems must transport water from the intake source to treatment facilities, then to local storage facilities, and finally to the customer. Most of the energy involved is used for pumping. Much of Kauai’s distribution system was placed underground more than 50 years ago, and leaks caused by corrosion of pipe material or other problems can lead to the loss of significant amounts of potable water. Distribution system losses increase the energy intensity of water
supply by requiring the Department to treat and convey water that will be lost. The Department reports that 25% of water is unmetered, this could unclude use for firefighting, construction, and flushing drains and hydrants.
Water loss should be tracked monthly to identify leaks or inaccurate meters to reduce energy cost associated with pumping and treating water that is not being sold. A monthly comparison should be made between the amount of water that is pumped and treated versus the water that is billed to customers. Water losses vary significantly among urban suppliers; typically from 6 to 15 percent with approximately 2 percent of this loss water goes to firefighting, and flushing drains
With a SCADA system continuously monitoring and managing variable frequency motor drive pumps that are more efficient under partial loads better control of water line pressure, which reduces leaks, allowing them to save both water and energy.
When planning water system improvements, such as main replacements, the pipe length, diameter, and roughness impacts the amount of friction in the main which translates to an increase in energy that is needed to move water from one place to another. Piping components and design, such as valves and unnecessary flow paths, can also impact frictional losses in the distribution system. When doing distribution system improvements it is important to analyze the initial cost
and the life cycle cost as they relate to energy efficiency.
During distribution water must be kept moving and under pressure to minimize corrosion and biological contamination. Storage tanks and water mainlines must be flushed periodically to prevent oxidation and control biofilms (AWAARF2000). Even the farthest reaches of the network must be kept under adequate pressure and constantly flushed since low pressure and low flow allow microbes to flourish.
There should be wastewater energy audit and/or technical analysis of facilities to determine the area of greatest need and most cost-effective energy saving opportunities. Being energy self-sufficient should be the goal.
One of the most critical features in a wastewater facility is the design of the plant. Unfortunately, this is one feature that most operators or managers have little control over, unless in the midst of a system upgrade. On Kauai the relocation of some wastewater facilities will be imposed by a rising sea level.
According to the Electric Power Research Institute, 95% percent of the electricity used for distribution and treatment in wastewater plans is due to motors used in pumping and aeration. Much of the pump efficiency information from the water pumping also applies here.
Wastewater systems generally include three components: collection systems (sewers and pumping stations), treatment facilities, and effluent disposal or reuse. Collection and disposal or reuse requires energy for pumping, while treatment requires energy for pumping, running treatment operations, and processing solids. Some facilities recover energy from biogas combustion, which reduces net consumption. Some wastewater facilities use anaerobic digester gas (ADG) production
cogeneration to increase energy production during on-peak periods.
Water conservation can reduce the energy required for treating wastewater and can eliminate the need to expand facilities.
Perhaps one of the most ancient wastewater treatment methods known to humans are waste stabilization ponds, also known as oxidation ponds or lagoons These are often found in rural areas where land is available and cheap. They utilize natural processes to "treat" waste materials, relying on algae, bacteria, and zooplankton to reduce the organic content of the wastewater. These lagoons require about one acre for every 200 people served. Mechanically aerated lagoons
only need 1/3 to 1/10 the land that un-aerated stabilization ponds require. It's a good idea to have several smaller lagoons in series rather than one big one; normally, a minimum of three "cells" are used.
Unless the Wastewater Department finds low cost, low-energy alternatives soon, it will likely find that $800 composting toilets have become the preferred option to their $100 a month sewer fees with their newly unemployed customers.
Other Renewable Resources
We need to start talking about occupying the landscape differently. What is called for are not "solutions" but "adaptations." One does not "solve" inevitable change, but one might adapt to it. The developable renewable energy potential owned by the water and wastewater departments is not yet known. It would be beneficial to identify, assess and prioritize these resources, and find the technical and financial assistance to help develop renewable
energy. In addition to micro-hydro generation, the Department could generate electricity through dedicated photovoltaic solar cells. Most buildings and water tanks are potential sites for photovoltaic solar generation. Third-party installations may have the most financial benefit.
After the dots are connected, what picture appears? An ominous one. The dark clouds of the perfect storm are starting to appear on the horizon. What makes this storm so destructive is the convergence of multiple adverse trends. Economic growth is hardwired into our financial system. Without economic growth the system will collapse. The engine of our economy runs on oil. Oil is a finite resource. Oil has peaked. The cheap oil is gone. Our President knows this. This is
why he took us to war. This war has been financed with debt. Our economy has been financed with debt. Our industrial base has been shipped to our competitors. Our ability to repay our debts will rely on the liquidation of our inheritance to our foreign creditors.
On Kauai we have become a one-industry economy. The tourism industry here is nearly totally dependent on low cost airfares that are totally dependent on cheap oil. This means the storm will hit here early and result in extremely high unemployment. These people will need to become farmers or leave the island.
A major concern is that we have polluted our atmosphere so much that we are seeing extreme climate changes. If we do not stop this pollution soon, we will reach tipping points that will cause cascading effects that we will not be able to reverse. Our planet Earth will resemble planet Venus. If the industrialized world turns to cheap coal to replace cheap oil then we have a very limited future for this planet. We have to find sustainable solutions to existing problems.
The good new is that Kauai appears to be a potentially seaworthy lifeboat in which to ride out this approaching storm. The bad news is that some re-structuring needs to be in place before the storm hits. Re-structuring to ensure that majority of our residents survive. The critical need is for visionary leadership. We need you to step up to get us shipshape posthaste.
The KIUC Board of Directors is consumed with budgetary matters to take the bold actions needed to kick oil dependence in a timely manner. The price of oil will become prohibitively expensive and KIUC could go bankrupt. There goes our sole source of power! We can live without lights, but we cannot live without water and food. If we are to have enough food, we must grow it ourselves. To grow enough food we must have irrigation water. If we are to have a future on this island
we must use gravity to supply our water. This was done in the past and it can and must be done again. It can and should be done better than in the past. The amount of water needed to have food self-sufficiency needs to be provided at costs that subsistence farmers could afford.
In times of emergency, rainwater collection systems, gray water recycling and composting toilets should not only be allowed but possibly mandated by law. This is the environmentally and morally right thing to do. The time to act is now. Please be brave. Please be the leaders we need now.