On-site Power for Data Centers: New Possibilities in a Changing Marketplace

Overview

The paper first contrasts paralleled and distributed (pod) generator architectures and their UPS ride-through implications. Distributed pods start without paralleling delay, so a flywheel UPS with 20-25 s ride-through can suffice, while paralleled systems usually use battery UPS for longer ride-through.

It then compares Tier 2 diesel, Tier 4 diesel, gas reciprocating engines and gas turbines on cost, efficiency, start and load acceptance, and permitted non-emergency hours. Stationary emergency (EPA Tier 2) diesels may run unlimited hours in emergencies but no more than 100 h per year for maintenance, testing and other non-emergency use. Diesels can be online and fully loaded within 10 s (NFPA 110) and accept a 100% block load.

Gas engines offer 40-44% electrical efficiency; units of 2.5 MW and larger may need up to 120 s to accept full load, while smaller 1,800 rpm units need about 60 s or less when ramp-loaded. Gas turbines start in 4-10 minutes and need combustor replacement after about 60,000 h. The paper also covers demand response, microgrids, CHP and business factors such as load characteristics and facility life.

Key points

1. Distributed pod systems start without paralleling delay; flywheel UPS with 20-25 s ride-through can suffice.
2. Paralleled systems usually rely on battery UPS for longer ride-through.
3. EPA Tier 2 emergency diesels: unlimited emergency hours, at most 100 h/year for maintenance, testing and other non-emergency use.
4. Diesels reach full load within 10 s (NFPA 110) and accept a 100% block load.
5. Gas engines: 40-44% electrical efficiency; 2.5 MW and larger may need up to 120 s for full load, smaller 1,800 rpm units about 60 s or less.
6. Gas turbines start in 4-10 minutes; combustor replacement after about 60,000 h.
7. Summary table: Tier 2 diesel under 100 non-emergency h/yr; Tier 4 diesel and gas engines 100+ h; turbines continuous duty.

Using it in design

• Give the generator module a prime-mover choice (diesel Tier 2 emergency, diesel Tier 4, gas recip, gas turbine), each with start time, full-load acceptance time and permitted non-emergency hours.
• If gas engines or turbines are chosen for standby, require UPS ride-through at least equal to their load-acceptance time.
• If demand-response participation is enabled with Tier 2 diesels, cap it at 100 h/yr.
• Offer architecture templates for a paralleled bus and a distributed pod.

Who should read it

Data-centre energy planners and designers weighing non-diesel options and demand-response participation.

Related standards

• NFPA 110
• EPA 40 CFR 60 Subpart IIII

Publication details

Authors

Michael A. Devine; Brian Jabeck

Publisher

Caterpillar

Year

2015

Document language

English

Source type

Manufacturer

Access

Free to read

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation