The New Logistics of Data Center Fuel Supply
Data Center generator fueling now is delivering lots of fuel to many individual generators. Data Center generator systems are now predominantly individual generators within enclosures with sub-base diesel storage tanks sufficient for design run times. Older data centers had generators in buildings with day tanks refilled from large remote bulk storage tanks. Why the change?
Cost and Reliability
Sub-base diesel tanks are installed directly beneath the generator, which means that the fuel can flow by gravity to the generator's engine. The fuel supply lines from the sub-base tank to the generator are shorter and simpler, which reduces the chances of fuel leaks, blockages, or other issues that can arise with longer fuel lines. A sub-base tank design eliminates the need for a fuel transfer pump and associated wiring, piping, and control systems, which can save installation and maintenance costs.
On the other hand, external day tanks are usually located outside of the generator room, and they can be located at a great distance from the generator. The fuel supply lines from the external tank to the generator are typically longer and may require a fuel transfer pump to lift the fuel to the generator's engine. The pump is responsible for transferring fuel from the external tank to the generator and maintaining the fuel pressure at the required level. Furthermore, the pump and its associated components require regular maintenance, such as filter changes, lubrication, and pump seal replacement, to ensure proper operation and to avoid fuel system failures.
The choice of a fuel tank and pump configuration depends on the specific requirements of the data center, such as the generator location, fuel consumption rate, and the available space. In general, sub-base tanks are a simpler, more reliable, and cost-effective solution for providing fuel to the generator engine, while external day tanks may require additional components such as a fuel transfer pump and associated piping, wiring, and control systems.
Environmental and Fire Safety
Sub-base diesel tanks are considered to be safer than external day tanks in regard to the environment and fire hazards for several reasons:
- Leakage risk: Sub-base diesel tanks are installed directly beneath the generator, which minimizes the risk of fuel leaks. The fuel lines connecting the sub-base tank to the generator are shorter and simpler, which reduces the potential points of failure that could lead to fuel leaks. In contrast, external day tanks are typically located further away from the generator and may require longer fuel lines that increase the risk of leaks or spills.
- Fire hazard: Sub-base diesel tanks are installed below the generator, which means that they are less likely to catch fire in the event of an external fire. Additionally, the sub-base tank's location reduces the risk of fuel vapor ignition, which can occur with external day tanks. This is because external tanks may be exposed to higher ambient temperatures and other ignition sources, which can create fuel vapor buildup and increase the risk of a fire.
- Contamination risk: Sub-base diesel tanks are smaller in size than external day tanks, which means that the fuel is used up more quickly, and the fuel supply is replenished more frequently. This reduces the risk of fuel contamination, which can occur when fuel sits for extended periods. Additionally, sub-base tanks are easier to inspect and maintain due to their central location, which allows for faster detection and remediation of any potential contamination issues.
Overall, sub-base diesel tanks are a safer option for data center backup generators, as they reduce the risk of fuel leaks, fires, and contamination. While external day tanks may be necessary in certain situations, they require additional precautions and maintenance to minimize environmental and fire hazards.
Solo-Fill and Fuel Polisher Versus Multi-Fill and Fuel Polisher
In a backup power system for a data center or any other critical facility, fuel quality is of utmost importance to ensure the reliable operation of the backup generators. One of the ways to maintain fuel quality is through the use of fuel polishers, which remove contaminants and impurities from the fuel.
The fuel system can be designed as a solo fill or multi-fill system, depending on the requirements of the facility. Let's look at the differences between these two systems:
- Solo Fill System: In a solo fill system, each generator has its own dedicated fuel supply tank, which is filled separately from the other tanks. This means that each tank is filled independently, and there is no interconnection between them. Similarly, each tank has its own dedicated fuel polisher system, which filters and cleans the fuel in that tank only.
The advantage of a solo fill system is that it allows for greater control over the fuel quality of each generator. Each tank can be filled with fuel of the exact specification required by the generator, and the fuel polisher system can be customized to meet the specific needs of each tank.
However, the disadvantage of this system is that it can be more expensive and complex to install and maintain since each generator has its own fuel supply tank and fuel polisher system.
- Multi-Fill System: In a multi-fill system, multiple generators share a common fuel supply tank, which is filled from a single source. The fuel is then pumped from the common tank to each generator's sub-base tank as needed. Similarly, there is a single fuel polisher system for all of the tanks, which filters and cleans the fuel for all the generators.
The advantage of a multi-fill system is that it is typically less expensive and less complex to install and maintain since there are fewer tanks and fuel polisher systems involved. It is also easier to manage the fuel supply since there is a single source of fuel for all the generators.
Both solo fill and multi-fill systems have their advantages and disadvantages, and the choice between them will depend on the specific requirements of the facility and the backup power system. Ultimately, the goal is to ensure reliable operation of the backup generators by maintaining the quality of the fuel supply.
Fuel Consumption and Predictions
The fuel consumption of a generator can vary depending on several factors, including the size and capacity of the generator, the load it is powering, and the type and quality of fuel being used. However, there are some general guidelines that can help you estimate how much fuel a generator is likely to consume per hour.
- Check the manufacturer's specifications: The manufacturer of the generator should provide information on the fuel consumption rate for the specific model. This information is usually provided in the form of a fuel consumption chart, which will give you an idea of how much fuel the generator will use at various load levels.
- Consider the load on the generator: The fuel consumption of a generator will increase as the load on the generator increases. As a general rule, a generator will use more fuel to produce a higher level of output. You can estimate the load on the generator by measuring the amount of power being drawn by the devices or equipment that are connected to it.
- Consider the fuel type: The type of fuel being used can also affect the fuel consumption rate of the generator. For example, diesel generators typically use less fuel than gasoline generators, and natural gas generators use less fuel than diesel generators. The quality of the fuel can also affect the fuel consumption rate, as lower quality fuels may contain impurities that can reduce the efficiency of the generator.
Once you have a good estimate of the fuel consumption rate for the generator, you can use this information to calculate how much fuel the generator is likely to use per hour. For example, if a 100kW generator has a fuel consumption rate of 10 gallons per hour at full load, you can estimate that it will use approximately 5 gallons per hour at half load (50kW), or 2.5 gallons per hour at a quarter load (25kW). Keep in mind that these are just estimates, and the actual fuel consumption may vary depending on the specific circumstances and conditions at the site.
Fuel Monitoring
If a facility has both multiple day tanks and large storage tanks, the fuel monitoring system will need to be designed to monitor the fuel levels in both types of tanks.
In this scenario, the fuel monitoring system will typically have sensors installed in each tank to monitor the fuel levels separately. The sensors can be either mechanical or electronic, and they are usually installed in the top or bottom of the tank to provide accurate readings.
The sensors are connected to a control unit, which is typically installed near the tanks or in a central location. The control unit continuously monitors the fuel levels in each tank and transmits this information to a central monitoring system. This monitoring system can be accessed by facility managers, technicians, or other personnel who need to know the fuel levels in each tank.
In addition to monitoring the fuel levels, the fuel monitoring system can also track other important data such as fuel usage rates, fuel deliveries, and tank levels over time. This information can be used to optimize fuel usage, schedule maintenance, and identify potential issues before they become problems.
If the facility has multiple day tanks, the fuel monitoring system will also need to track the fuel levels in each tank separately. This allows facility managers to know how much fuel is available in each tank and to transfer fuel between tanks as needed to ensure that the generator always has an adequate supply of fuel.
A fuel monitoring system that is designed to work with both multiple day tanks and large storage tanks is an essential tool for managing generator fuel supplies in large facilities. By providing real-time information on fuel levels and usage rates, the fuel monitoring system can help to ensure that the generator always has an adequate supply of fuel to keep the facility running smoothly.