Anderson Hungria serves as senior UPS product manager for Active Power.
Data center operators are always aiming to boost profit margins and make the most out of their investments, especially with products that are designed to last up to 20 years. Total cost of ownership (TCO) is a key factor in realizing energy and cost savings over the life of any electrical product, such as a UPS. TCO is the total cost needed to purchase (capital expenses or CAPEX) and operate and maintain (operational expenses or OPEX) a product or facility. Since data centers consume a tremendous amount of energy, any reduction in energy consumption directly affects the bottom line, and that starts with the electrical infrastructure – primarily the UPS.
Let’s evaluate four essential factors to calculating the TCO of a UPS – from initial purchase and installation cost to UPS efficiency, cooling needs and required maintenance and component replacement. For consistency and transparency, all of the comparative figures highlighted throughout the article are based on the following scenario and assumptions.
- Four flywheel UPS systems compared to four double conversion UPS systems with four standard battery cabinets each deployed in parallel
- Both flywheel and battery UPS systems are rated at 750 kVA / 0.9 power factor
- 7 megawatt of total UPS capacity protecting a 1 megawatt load
- UPS systems operating at 40 percent load for redundancy
- Flywheel UPS has an efficiency rating of 96.5 percent vs. 93 percent for battery UPS
- Battery UPS includes battery monitoring per cabinet
- Initial cost and startup and installation costs are identical for both systems
Initial Purchase and Installation Costs
The initial cost of a UPS is only a small part of the equation of owning and operating an efficient and profitable data center. Aside from the UPS itself, the choice of energy storage and electrical infrastructure is also very important to determine the overall initial purchase and installation costs.
Keep in mind that in many instances the lowest initial cost solution is not the best long-term decision. An integrated flywheel UPS, for example, does not require costs associated with purchasing battery cabinets, battery monitoring and additional safety and cooling provisions, thus delivering a lower TCO at a competitive initial cost.
Even when the initial cost of a double conversion UPS is lower, about 40 percent of the initial price is associated with batteries that will have to be replaced in four to six years depending on usage and maintenance. Battery installation can be another large and time consuming initial expense. In comparison, more than 95 percent of the initial investment (capital expense) of an integrated flywheel UPS will never have to be replaced.
While the initial cost of a UPS is certainly important, TCO evaluations need to be balanced and long-term operational, maintenance, and replacement costs considered. Operating costs can quickly exceed the initial investment of a UPS. Now, let’s take a look at those factors that will affect operational costs.
Efficiency plays a significant role in energy and operating cost savings of a UPS over the life of the product. The higher the power demand, the higher the savings, even with a 1 or 2 percent efficiency gain. A high efficiency UPS is a must for today’s energy saving and green mentality; however, two important aspects must be considered:
- What is the UPS efficiency at the actual rated load?
- What is the level of protection or mode the UPS is operating in?
First, UPS efficiency is load dependent and not a linear relationship which means UPS efficiency curves will dictate the correct efficiency at a rated load. For traditional UPS loads in the 40-50 percent range, a conventional double conversion UPS efficiency is approximately 93 percent versus an integrated flywheel UPS at approximately 96.5 percent.
Secondly, it’s important to assess the UPS operating mode. Eco Mode or high-efficiency mode can offer 98-99 percent efficiency; however, these modes don’t offer the same voltage regulation and protection as normal or online mode. An integrated flywheel UPS can offer up to 98 percent efficiency and maintain +/- 1 percent voltage regulation and protection to critical loads at all times while delivering significant savings over time.
Over a 10-year period at 96.5 percent efficiency, an integrated flywheel UPS can deliver savings of more than $300,000 when compared to a battery UPS operating at 93 percent efficiency.
After servers and computer equipment, cooling represents about 30 percent of a data center’s energy usage. Many techniques are currently implemented to reduce cooling costs including hot/cold aisle containment, economizers and free-cooling. When it comes to the UPS, energy savings and low TCO can be realized by choosing a UPS that can operate in higher ambient temperatures and has low heat dissipation. UPS batteries must be kept at 77 F requiring a tremendous amount of cooling equipment, and, in some cases, dedicated battery rooms. One major advantage of a flywheel UPS is the fact that it can operate in environments up to 104 F with no degradation to performance, lowering overall cooling requirements by almost 50 percent. For a data center with a 1 megawatt load, cooling savings can exceed $100,000 over a 10-year period.
Maintenance and Component Replacement
Data centers are like living organisms and require a significant amount of maintenance in order to ensure high reliability and availability to critical loads. For conventional UPS products, batteries need to be checked two to four times annually while an integrated flywheel UPS requires only one preventative maintenance event per year. Minimizing maintenance frequency will lower operational expenses and reduce the possibility of any downtime caused by service or potential human error.
As part of most maintenance contracts, the periodic replacement of certain components such as batteries, bearings or DC capacitors is usually included. These are all additional costs that some data center managers wish they could avoid regardless if they are treated as a capital or operational expense. Since a flywheel UPS does not rely on batteries, the system can offer the lowest TCO in the market when it comes to replacement costs. Batteries are normally replaced after four to six years of usage, so in 10 years a data center can expect two battery replacement cycles at a total cost of approximately $750,000.
Based on the assumptions outlined earlier, overall TCO savings is approximately $1.5 million over a 10-year period for an integrated flywheel UPS versus a conventional UPS with batteries.
The typical lifespan of a UPS product (not the battery energy storage) can approach 20 years, which is a long time to be paying for ever-increasing operating costs, particularly if the system is inefficient and requires lots of maintenance. How do we prevent these costly mistakes?
Do your homework. Question your vendors. Request TCO models and have the vendor walk you through the numbers. Only then will you see the possibility of saving a substantial amount of money over the life of the UPS.
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