The Coolest, Most Bad%ss, Great Geothermal Marketing Video Ever Made

Thanks to Energy Smart Alternatives for creating this video and posting it on twitter, where I found it, while I was stalking you.

To give credit where credit is due, Love’s Geothermal down in Maryland also has an amazing “story of a geothermal installation” and some great videos of full installations, like this one below.

If you […]

July 18th, 2012|Categories: Geothermal Heat Pumps, Solar Sales & Marketing|Tags: , |

“What’s the Most Efficient?” Geo VS Solar Thermal VS Solar PV

 I’m doing some sales consulting work in NYC, and there’s one question I’m getting a lot from property owners: “What is the most efficient renewable energy technology?”

In the city, they are mainly speaking of solar PV vs solar thermal, because generally there’s not enough room for geothermal in the city. However, for fun, I’ll expand it and include geothermal.

The answer is, of course, it depends on how you’re defining efficient.

 Which technology produces the most energy in the least amount of area
Which technology produces the most valuable energy
Which technology has the best financial return. Again, however you’re defining return.

There are two ways that I’m going to frame the discussion to search for an answer, or a methodology for finding an answer: 

 Efficiency of the technology (is this a good design for this specific application)
Efficiency of cash, which takes into consideration the site characteristics and policy (is this a good investment?)

As always, it’s easiest to see this when we look at a few examples, being clear to highlight when and where the examples might be different in the real world and how said sensitivity might impact our results.

1. Technology Efficiency. Right now, let’s just look at GROSS INSTALLED Costs and raw energy production. 

Here’s what I’m going to calculate: Gross Installed cost / Net energy produced in year 1 (energy produced / energy used)

Again, I’ll keep it in residential for simplicity. And I’ll focus on Boston because I’m most familiar with the solar resource available and the average heating degree days needed when understanding geothermal production.

Our example home will be:

1500 square feet
Average home shell construction.
South Facing roof, no shading, 10 pitch, that is 60 feet by 12 feet.

Solar PV: $25,000 /  6,843 kWH produced per year = 3.65, which means that you must invest 3.65 dollars in year 1 to get 1 kWh of production

5kw DC Installed @ $5.00/watt  = $25,000
Avg Insolution = 5 hours of full sunlight per day.
We’ll derate from DC to AC is .75, which is extremely conservative.
AC Production = 3.75 AC output
3.75 X 5 hours per day = 18.75 kWh production per day on average.
18.75 X 365 = 6,843 kWH produced per year

$25,000 /  6,843 kWH produced per year = 3.65, which means that you must invest 3.65 dollars in year 1 to get 1 kWh of production

Solar Thermal: $8,000 / 4,982kWh = 1.6. For every $1.6 dollars invested you get 1kWh of production.

3 to 4 family home
Gross Installed Costs for a simple drawback system by a well trained crew is ~$8k
Each Module will likely produce around 85 therms per year, totally 170 therms per year
170 therms is 17,000,000 BTUs / 3,412 = 4,982 kWH equivalent.
$8,000 / 4,982kWh = 1.6
For every $1.6 dollars invested you get 1kWh of production.

Note: For solar thermal, unlike solar PV, production of solar energy and usage of that energy doesn’t necessarily match. For this example, I’ll assume it does.

Geothermal: $27,000 / 13,478 kWh equivalent = 2. You must invest $2 in year 1 to get 1kWh of energy production.

We’ll assume the heat pump is only heating, to make the calculation more simple and keeping in mind that our ratio of dollars invested to energy produced will be a little larger, if we considered cooling.
63 MBTU average heating load
Avg COP of 3.75 (this is important, because lower efficiency will increase the tonnage needed for the same btu’s delivered, all else equal)
3 Ton system
9k ton X 3 tons = 27k
Energy Produced = 63 M BTU –> Let’s convert BTU to kWh equivalant
63 M BTU = 18,463 kWH (Remember that 1kWh = 3,412 BTUs. Thus long calc is 63MBTU = 630 Therms (10 therms = 1MMBTU) 630 therms = 63,000,000 BTUS divide by 3,412 = 18,464)
Many will point out that geothermal uses energy (in pumps and fans) to produce more energy, which is true. However, we want to find out what EXTRA energy that was created by the system, this is the renewable part. With an average COP of 3.75 it means that 3.75 units of energy was created for every equivalivent energy put into the system.
3.75 means we need to reduce the energy produced by 26.66% (1 / 3.75) to find the amount that was produced by the system.
18,464 X 73% = 13,478 kWh equivalent produced
27k installed costs gross / 13,478 kWh = 2 in equivalent energy produced. Which means, that for you must invest $2 in year 1 to get 1kWh of energy

Here is our conclusion about gross installed costs and energy produced: 

Solar PV: $25,000 /  6,843 kWH
Solar Thermal: 8,000k / 4,982 kWh
Geothermal: 27k installed costs gross / 13,478 kWh

A few things to note about the sample examples

PV: $5 a watt is average and there are much higher installed costs.
Thermal – Production of modules and usage don’t necessarily match. Also, assumptions around water usage are not accurate. ~8k is also for a great site and a well trained crew. It’s common to see $10k+ projects.
Geothermal – Only assumed it was heating. Assuming 72 set point and 62MMBTU needed to heat the home. 3.75 COP also impact the energy produced from that invested cash. Higher COP = greater output, all else equal, per dollar invested.
As we’ll discuss in section 3, site characteristics can change the analysis of any one of these by making some technologies, cheaper or non-available in certain areas.

[…]

Geothermal Loop Design: Series vs Parallel Flow Path Analysis

When designing geothermal ground loops, this is an issue that a lot of people get hung up on. Because of the advantages of, we use parallel circuits in ground loops almost exclusively in our industry. Read more to hear why.

When loops are tied in series with one another, they will all see the full system flow rate (because there is only one flow path) and the pressure drop through the loops add together. Because there is only one flow path, the pump must overcome the pressure drop through each consecutive loop as the fluid travels through the system from the supply to the return line.  The pump will be required to produce the combined pressure drop from the series loops at a shared flow rate.

In a parallel system, the flow through each loop will be the same. We add individual loop flows together to get the combined total system flow rate on the supply-return line back to the heat pump. The amount of pressure required to overcome friction losses through each loop (because they equally share the total system flow) will all be the same.  The pump will be required to produce the combined flow rate from the parallel loops at a shared pressure.

To Summarize:

In a series system, the total length of the well pipes would have to be figured in calculating head loss while in a parallel system only one loop needs to be calculated.

Parallel flow: Individual loop flow rate adds at a common pressure drop

Series flow: Individual loop pressure drop adds at a common flow rate

Series system

Advantages include: Single flow path and pipe size, higher thermal performance per foot of pipe, since a larger diameter pipe is required.

Disadvantages include: Larger water or antifreeze volume of larger pipe, higher price per foot of piping material, increased installed labor cost, limited length due to fluid pressure drop and pumping costs.

[…]

What You Need to know About Quoting and Selling Standing Column Well Systems

It’s much easier to answer this question for residential applications.  The price is composed of three pieces:  the drilling cost, the loop field installation including underground piping to/from the building, and the HVAC system installation. Many times the driller is also the installer, but not always.  Sometimes the mechanical contractor controls the overall bid.  In general, here in the SE PA area prices for the geothermal installation are running between $12/ft to $14/ft.  There is another $1600 in the trenching, penetration, backfill, grading & re-seeding. So, for a typical 2500 sf home, one might expect to pay around $15,000.  The extended range (4 ton) heat pump installation, circulator, water/methanol fill, and commissioning might add $8000 for a total price to the owner of $23,000.  This could be higher or lower based on the thermal conductivity of the site and how easy or difficult it is to drill and contain the spoils.
Download the 13 Steps Basics Steps to Standing Column Well Design to get a better understanding of how design overlaps with quoting projects
Read more to get more information on quoting SCW projects.

[…]

13 Steps to Basic Geothermal Standing Column Well Design

HeatSpring Instructor Albert Koenig discusses the 13 steps to basic Geothermal Standing Column Well (SCW) Design…

Unlike closed loop geothermal installations, open loop systems, in particular, standing column well (SCW), require more diligence from the designer than just the well field.  In the former case, the HDPE supply and return pipes are handed through the foundation […]