Christian Mueller is a sales engineer at Minnesota-based MTU Onsite Energy.
Combined heat and power (CHP), also known as cogeneration, is the simultaneous production of heat and electric power from the same source of fuel. From data centers to universities, interest in CHP systems as sustainable standby power supply is rising.
Historically, CHP was reserved for very large installations. For example, waste heat from a coal-fired power plant could be used for greenhouses or large apartment complexes. Today, significantly smaller facilities, such as hospitals, hotels, commercial buildings, and some data centers are reaping the benefits of utilizing heat that would otherwise be wasted from the production of electricity. Because CHP systems require less fuel than separate heat and power systems, a reduction in operating cost, despite rising energy cost, is guaranteed. Over the long term, CHP can significantly reduce energy expenditures that can be applied to the bottom line—as long as there is a simultaneous need for electric power and heating (or cooling) for most of the year.
In a conventional data center, all electrical power is supplied by a local utility. If heat is needed, the facility would have a gas-fired boiler to supply hot water for space heating or process heat. Additionally, separate water heaters running on natural gas or electricity would provide hot water to the data center. In contrast, a facility with a properly sized CHP module running on natural gas would supply most of the electrical and heating loads, cutting grid energy usage and expenditures.
The concept of uptime is not a new one for data centers. The Uptime Institute was developed in 1993 to set global power design standards while improving reliability and uninterruptible availability—uptime—in data center facilities. It is often best described as the opposite of downtime—when a system becomes inoperable for any number of reasons, including malfunction, scheduled maintenance or a decision by the operator not to run a unit. Unexpected downtime can result in significant loss of business and revenue, and for data centers, critical information is put at risk during downtime.
To avoid downtime, it is important to first identify its causes.
Causes of Downtime
Natural Wear and Tear: It should come as no surprise that simple wear and tear can create unexpected downtime. There is not much that can be done to prevent downtime in these cases, but the first line of defense is preparation. The goal of any instance of downtime should be returning to uptime as quickly as possible. Operation training can be a key factor in this. As the first person that arrives during a shutdown, the facility operator should have some basic troubleshooting knowledge of the system. Also, it is important to establish a Long Term Service Agreement (LTSA) with a local distributor from the start to ensure a record of parts and their scheduled replacement timing. The fixed cost of an LTSA can also help control overhead spending for a facility.
Ambient Conditions: Certain climates create harsher ambient conditions than others. With proper planning, downtime because of hot or cool temperatures, or extreme altitude, is lessened. Designing a CHP should be customized to ambient conditions.
Fuel: CHP modules are dependent upon fuel arriving through a pipeline. Many factors can affect operability. In addition to ensuring optimal pressure, operators must safeguard the composition of fuel. Impurities like sulfur and siloxane can contaminate the engine if above ideal limits, leading to corrosion. To combat against this, gas treatment cleaning systems are needed to remove contaminants before they reach the engine.
Demand of Output (Electricity and Heat): Appropriately sizing a CHP for the specific application has a major impact on system reliability. CHPs are designed to run when needed, meaning a 50-100% load is the optimal operating range and a load between 80-100% load is where the greatest efficiency is achieved. If there is a large range in electricity load, sizing becomes even more critical to carry those wide ranges. Careful load match is key to ensure the unit is not over- or under-sized.
Peripheral Equipment: Heat recovery, cooling, ventilation, electrical and control systems are examples of peripheral equipment that help a CHP operate. Operability of a CHP is dependent on this complex network of highly engineered modular pieces and components communicating and working together seamlessly. For example, if the sizing is incorrect on one piece of equipment, the entire CHP unit suffers.
Scheduled Service and Maintenance: As with any standby power system, CHP modules require regular service and maintenance at the recommendations of the manufacturer. Scheduled parts updates, visual inspection, hose replacement, filter changes and other routine systems checks safeguard against downtime. Parts availability is also integral in system maintenance. In order to maintain uptime, it’s important to have various levels of stocked parts in close proximity to the unit.
Support from a trained technician with mechanical and electrical systems knowledge is vital. Operators and technicians should undergo specialized training based on manufacturer specifications for a unit’s generator, engine, controls and heat recovery system to be fully prepared for the inevitable.
Even with capable on-site support, remote access is recommended. Web access is ideal as it grants the manufacturer access to the control unit from anywhere in the world. With the ability to view key information, such as operating conditions, power output and other historical data, the factory can troubleshoot many issues remotely, helping return to uptime quickly.
Reliability and continuous uptime is central to every data center. Power disruptions can cost more than $1 million a day in lost revenue for some enterprises. As a key factor in the economic viability of a business, ensuring power reliability is imperative for data centers that demand continuous power 24 hours a day, 365 days a year. Preventative planning measures, contingency planning and establishing a collaborative relationship with the factory and local distributor will ensure continuous uptime and availability of a CHP system.
Industry Perspectives is a content channel at Data Center Knowledge highlighting thought leadership in the data center arena. See our guidelines and submission process for information on participating. View previously published Industry Perspectives in our Knowledge Library.