Grassy Mountain Case Study

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Grassy Mountain Installation in Southwestern Colorado

Grassy Mountain Case Study

This electrical system was built and installed for a county application in Southwestern Colorado as part of a project to improve emergency communications in the area. The site is located 9700’ in elevation up a narrow and steep ATV path. An 800mZ repeater radio is the major load on-site with additional DC and AC power provided for local emergency service – fire, rescue and police - communication.

The combined load of all the communications systems is just over 50kWh per day – roughly equivalent to the electrical demands of two “average” grid connected homes. Not surprisingly the mandate for this electrical system was “extreme reliability” so two sources of power generation are available at the Grassy Mountain site. A 13.86kW PV array is the prime source of energy and it is backed up by a 20kW diesel generator.

The heart of the system is the Argus 400 Amp Hybrid Power Plant which integrates input from the solar chargers and the AC powered rectifiers into the DC bus. The PV array is divided into four sub arrays each feeding an Apollo T80 MPPT charge controllers – these are connected together in a masterslave network which allows them to share common settings. The slaves communicate energy harvest information to the master.

The solar system on this site is not intended to meet 100% of the power requirements, it was designed to meet 86% with the remainder of the power coming from the 20kW diesel generator which is on site. The 240Vac output of the generator is converted into 48Vdc by a bank of Argus Cordex™ 3.6kW rectifiers. The hybrid nature of this system – PV assisted by a generator – maximizes battery life and minimizes the risk of loss of load.

Grassy Mountain Case Study

System Specifications
Modules:	ASM 165 84Vmp 34.8Vdc
Array:	42 Strings of two modules
	13.86 Kilowatts
Racking:	14 Top of pole mounts
	Custom engineered to withstand 125mph wind load
	14 top of pole racks each holding 6 modules (3 strings)
Combiners:	4 12 String Combiners
	3 are fully populated with the output of 4 mounting frames
	1 is half populated as the system has room for expansion
Controllers:	4 Apollo T80 MPPT Controllers
	1 for each Combiner
BOS:	Argus 400 Amp Power Plant
Power Conditioning:	5 3.6kW Argus Cordex 240 to 48Vdc rectifiers
	120Vac INEX 1000VA inverter wired in parallel
	1 48 to 24Vdc converter
Batteries:	48 2Vdc 2 YS-31-PS cells
	6030 Amp hours @ 72 hour rate connected in two strings of 48Vdc

Document Downloads

Title	Type	Version	Date
Hybrid Power System - Grassy Mountain Case Study	Case Study	049-219-15-002	November 30, 2009