Page 15 - Advanced Technology for Energy and Water Saving

ENERGY USAGE

² HEAT PUMP “MINI-SPLITS”

A Path to Net Zero

Getting to net-zero energy consumption is within easy reach,
by combining solar PV with efficient heat pump technology
A the best new DC-to-AC inverters, made by companies

FEW MONTHS AGO, we spoke to builder Gene
Myers of Thrive Home Builders in Denver
such as SMA, can’t overcome the inconsistency of how
about whether mini-split heat pumps could
weather patterns affect PV power generation. According
be powered by solar PV panels, essentially
to Zach Nugent of ReVision Energy° in Portland,
converting electricity into affordable, clean
Earth’s rotation) mean that power output from PV is
heating and cooling for homes.
“We’re doing that on all of our new homes,” Myers told Maine, weather and seasonal issues (along with the
not consistent enough to take over the high demand
us. “We have been for a couple years now.” of a mini-split system’s outdoor condensing unit. This
At the time, our staff hadn’t looked closely at how such limitation applies even to a super-e‘cient model with
a marriage of technologies would work. Since then, we’ve a seasonal energy e‘ciency ratio (SEER) of 15 or more
been putting the pieces together. What we’ve learned is that and an energy e‘ciency ratio (EER) of 12.5 or more, with
the path to net zero with solar heating/cooling is possible, variable output.
but the devil really is in the details. For example, the outdoor component of a multi-zone
(three mini-split) Mitsubishi system draws about 3,800
INDIRECT, NOT DIRECT POWER—WITH RARE EXCEPTION watts at peak demand. A 6-kW solar array will sometimes
It’s important to understand that with only one product deliver that wattage and more—but not consistently.
exception that we know of, the ACDC12C, solar PV panels This need for a buffering technology narrows the
do not directly power mini-splits—at least, not yet. Even options for residential solar, and also explains why so

COST OF HEATING COMPARISON

Heat pump are less than half the cost to operate vs. the equivalent oil or program system
on a per BTU basis. This chart gives you a quick breakdown of relative costs.

Fuel Source Cost per Unit Cost per Million BTUs Cost of Heat Typical Home

Electric Baseboard $0.14/kWh $44 $4,489

Propane $2.73/gallon $40 $3,873

Heating Oil $2.70/gallon $25 $2,421

Heat Pump $0.14/kWh $18 $1,706

Heat Pump with Solar $0.09/kWh $11 $1,023

Based on fuel data and pricing from Maine Energy Office. Assumes typical boiler operating at 65% efficiency, propane at 85% efficiency,
resisticv electric at 95% efficiency and heat pump at 250% efficiency (COP of 2.5). Solar PV kilowatt-hour cost of 8.5 cents per
kilowatt-hour based on typical pricing economics of a 4kw + system.

ADVANCED TECHNOLOGY FOR ENERGY AND WATER CONSERVATION 15