The economic and environmental benefits of Combined Heat and Power (CHP) are well known. What is less understood is the extent to which CHP can, in many cases, take the place of conventional standby gensets. In these instances, it is only the incremental additive cost for CHP that must be justified--and given the reliability and efficiency of CHP, that payback can be very rapid.
If you are involved in a project that incorporates new standby gensets, CHP can be an excellent alternative. It's "Standby Power with Benefits."
Here are the Primary Advantages of CHP:
We feel that the best way to celebrate the New Year is to re-visit our BLOGs and directly thank our clients for working with us to provide on-site distributed energy systems and H2S removal solutions. Here are hyperlinks to the BLOG topics we have covered in the past:
. . . that's the classic dilemma with wet scrubbers. Sure, they're capable of removing soluble gases (such as H2S and SO2) from an exhaust stream, but then you have to contend with treating the acidic effluent prior to discharge or recycling. A better approach is to deploy a "dry" or "iron sponge" scrubber. Hydrated iron oxide on a carrier of wood fiber has been used for more than a hundred years to treat gas streams. The basic reaction is:
As you can see, iron oxide reacts with H2S, in the presence of moisture, to yield iron sulfide and water vapor. However, iron oxide would get so bound up with sulfur in the form of iron sulfide that it's efficiency would degrade relatively quickly. Fortunately, iron sulfide can be "regenerated" back into iron oxide with the addition of oxygen, as follows:
Introducing oxygen to the filter media converts iron sulfide to iron oxide and elemental sulfur. The regenerated iron oxide is then fully capable of capturing more H2S. The most efficient way to regenerate filter media is "offline"; that is, one filter vessel is active, while another is being regenerated. This is also the best option for processes that cannot tolerate oxygen, such as RNG upgrading.
Eventually, filter media accumulates enough elemental sulfur that it must be replaced. However, spent media is nonhazardous: it passes the U.S. EPA TCLP standards, is not "readily ignitable" per OSHA, and may be composted, land applied, or disposed of in any landfill.
Iron sponge scrubbers are available from a number of suppliers, but MV Technologies takes the concept a huge step further by adding biological agents to the media to remove numerous non-sulfur bearing species such as VOCs and readily biodegradable organic compounds. MV calls this enhanced media "BAM." BAM media also provides improved re-oxidation of the iron sulfide, which extends filter media life. For example, conventional iron oxide media has a loading capacity of about 0.12 lbs. of H2S per pound of media, while BAM offers a capacity for 0.29 lbs. of H2S per pound of media. This is an iron sponge scrubber on steroids and is why MV Technologies has retrofitted many competitor's systems to use BAM media.
Thus, this technology is usually the most cost effective solution for any H2S removal project for gas conditioning or odor control. Please make an appointment to talk to us for more information, or assistance with any ongoing CHP or H2S Removal applications.
The physics of sound, and the underlying math, can be challenging to grasp. For those of you that really need to immerse yourselves in the details, here is a nice little article that should suit your purpose.
For our purposes here, it's sufficient to note that while CHP has many benefits, being inherently quiet is not one of them. So unless your CHP project is located in the middle of nowhere, you may have to contend with managing its noise.
Here's a quick summary of common environmental noise measured in dBA (the "A" weighting takes into account that human hearing is more sensitive to certain frequencies):
Our default containerization attenuates sound to <65dBA@10m. Even this is pretty quiet--you could easily chat on your phone standing right next to the unit. However, there's a "Super-Silent" option that attenuates to <52dBA. This reduces sound by more than half (remember that the decibel scale is logarithmic).
Do you need to place the CHP unit right outside an executive conference room window? Sound attenuation options are available to accommodate that as well:
Please make an appointment to talk to us for more information, or assistance with any ongoing CHP or H2S Removal applications.
In our last blog we talked about the differences between a "modified" ISO container, and an enclosure properly designed and optimized for CHP (to review that article, click here).
But "proper design" might have to address issues other than ventilation, illumination, and clearances. For example, will the enclosure be sitting at a remote landfill, or outside the windows of hospital patient rooms? Is acoustics an issue? What about aesthetics?
There are many enclosure options available to accommodate all these scenarios.
Here's a sample:
So, no matter where a CHP plant needs to be located, containerization options are available to accommodate those needs.
Please contact us any time for more information, or assistance with any ongoing CHP applications.
When you think of "containerized CHP" does something like this come to mind?
You're looking at a "modified" ISO shipping container. ISO containers are commonly used as CHP enclosures because they do have one great advantage--they're cheap. Way more of these things are shipped to the USA from Asia than the USA can ship back, and they're piling up here.
But are they suitable for cogeneration enclosures? Let's take a look:
Other factors to consider:
Please contact us any time for more information, or assistance with any ongoing CHP applications.
Here's the scenario: You have:
Fortunately, there are several proven techniques for separating H2S from a gas stream. What might be surprising is that the unit cost of H2S removal (i.e. the cost/lb of H2S removed) can vary profoundly between those available technologies. Here's a summary (with notes that affect cost of ownership):
Bottom line? With 2000scfm and 1000ppmv H2S reduced to 25ppmv, the difference in media cost alone is more than $312,000 annually:
Of course, no single technology is best for all applications. And they're not mutually exclusive, either: For example, a dedicated, low-cost means for H2S control may make sense ahead of activated carbon if there are other contaminants (like siloxane) that must be removed as well.
Please contact us, and we'll help with your analysis to determine which approach represents your most cost efficient option.
Tables courtesy of MV Technologies, Inc.on for H2S is available; however annual costs increase dramatically for inlet concentrations greater than 200ppm.
2) Includes costs of nutrients and estimated labor for active system control.
3) MVNet™ systems provide for media changeout without confined space entry.
4) Media sets up "solid" if run to full life, making removal very difficult - often requires hydroblasting.
5) Vacuum truck removal is typical.
6) Active bacteria is sensitive to temperature, nutrients, pH and other environmental conditions. Systems may require up to 10 days to start and stabilize after shutdown for maintenance. Fluctuating H2S concentrations pose operating problems. If H2S "spikes," and the bacterial action may not respond quickly enough to maintain required outlet concentration. If inlet H2S is too low, bacteria population can "starve" and reduce effectiveness. Sulfur bearing effluent must be handled/managed and may pose additional water treatment considerations.
The tables applies mainly to applications that involve up to 300 lbs/day of H2S removed. Other well-known technologies may be appropriate for H2S removal for much larger flow rates. These include: caustic scrubbing; caustic scrubbing with biological conversion of the H2S; and iron based liquid "redox."
CHP offers high energy efficiency, and can generate revenue (or avoided cost)...but that benefit is offset by capital and O&M cost. How do all these variables interact? What are the decisive factors on the bottom line?
The economic yield (NPV) of any CHP project is driven by these Economic Factors, in this order:
1. Operating hours per year
2. Electrical efficiency
3. Maintenance cost
4. Capital cost
The chart below shows how each of those Economic Factors affects the Economic Benefit (e.g. NPV or ROI):
A. CAPITAL COST: Lower capital cost is desirable, right? In reality it has far less effect than you might think. As you can see, as capital cost increases, NPV decreases SLIGHTLY:
A 50% increase in Capital Cost yields only a 3% decrease in Overall Economic Benefit.
B. MAINTENANCE COST: Surprisingly, the cost of maintenance doesn't IN AND OF ITSELF have much effect on economic performance (of course, if you're down for maintenance you're not running either--see item D below). So it's better to pay for overtime labor or FedEx a part if it means getting UP AND RUNNING faster.
C. ELECTRICAL EFFICIENCY: Here's where the rubber meets the road:
Improving efficiency from 35% to 41.5% improves economic performance by 14.8%.
Every point counts.
D. OPERATING HOURS: The most important factor of all is to keep the system running.
The difference between 7000 and 8300 operating hours per year translates to a 16.7% increase in economic benefit.
The best CHP providers offer minimum guaranteed annual operating hours, and minimum electrical efficiency -- but many don't. These principles will help assure maximum economic returns on your next CHP project!
If you want or need the power of onsite distributed energy generation,TransEnergy can provide the necessary CHP project economic analysis and applications engineering as a no-charge component of the manufacturers products we distribute.
Please contact us any time for more information. Thank you very much!
George Voss is a Partner with TransEnergy LLC and Founder/President of Sustainability Business Management. George, a sustainability, distributed energy, & environmental expert, an innovative leader and entrepreneur, offering his expertise to help manufacturers, reps and distributors better understand customer benefits associated with their products/services and realize growth objectives.