Sustainable Industrial & Commercial Heating Solutions – A Critical Pain Point
No, this blog post is not about those hot problems. It is about problems companies, especially in the manufacturing sector, face for their heating requirements!
With the prices of furnace oil, diesel and LPG increasing alarmingly in the past few years, companies suddenly find their costs of their energy shooting up to unaffordable levels.
Suddenly, using renewable and sustainable energy sources such as solar and biomass, and utilizing heat that was wasted earlier appear to be the way forward.
I hence thought I’d provide an overview of renewable and sustainable options available for heating requirements in factories.
The following are the sustainable heating avenues that are technically feasible today:
- Solar Water Heater
- Waste Heat Recovery/CHP/Cogen
- CST (concentrating solar thermal)
- Energy efficiency heating equipment
- Back pressure steam turbine
Solar Water Heaters
Yes, we are talking about the simple and common solar water heaters.
Could they provide a solution for industrial heating needs?
The answer is Yes.
Solar water heaters typically can provide temperatures up to only about 70OC, while many industries such as food and diary will require temperatures upwards of 150 deg C.
This should however not be a deterrent as solar water heating can be used to preheat the water. To the extent that solar water heaters can be used to replace furnace oil or diesel, proportionate cost savings can be derived.
Taking the current prices of furnace oil, diesel, LPG or natural gas, even partial substitution of any of these fuels with solar heat makes significant economic sense. The capital cost involved in setting up this solar water heater facility can be recovered in about 2.5 years at the current prices of fossil fuels.
Biomass based heating
Let’s consider a factory currently using about 10000 m3 of natural gas per day (or about 10,000 liters of furnace oil per day) for this discussion. Such a factory can save considerably by switching over to biomass from fossil fuels for its heating applications.
The advantage with biomass based heating is that it is a firm source of energy and can technically replace the entire fossil fuel use for 24X7 operations.
Biomass–based heating is a fairly old idea, but today, this can provide more bang for the buck using the gasifier technology which is a much more efficient way to provide heating than direct combustion. Essentially, combustion is not the best way to derive heat energy from biomass. Gasification, by first converting the biomass into an organic gas called the producer gas, makes the entire heating process far more efficient as it is easier to control and optimize producer gas for combustion than it is to optimize raw biomass.
Using gasification also provides small amounts of charcoal as a by-product. Charcoal commands a good value in the marketplace.
Today, a number of plants in India and overseas are seriously looking at using biomass for their boiler as well as their other heating and drying applications.
The economics of biomass are fairly simple. At the current prices of biomass (Rs 4-5 per Kg), a 50 T per day biomass based gasification can displace about 10000 m3 of natural gas or about 10,000 l of furnace oil. Natural gas costs about Rs 40 per m3 and furnace oil about Rs 42 per liter.
Thus, biomass based heating would cost Rs 2.5 lacs per day vs Rs 4 lacs approx for either furnace oil or natural gas. This translates to a saving of Rs 1.5 lacs per day for such a facility or over Rs 5 crores per year!
The payback periods for these are in the range 2-3 years.
Waste heat recovery / CHP / Cogen
Utilization of waste heat has become one of the most sought after ways in the manufacturing sector today. With available technologies, it is today possible to convert both high temperature waste heat as well as low grade waste heat into useful heat or cooling.
Of specific relevance here are technologies such as vapour absorption chilling, stirling engine and organic rankine cycle power generation mechanisms. While stirling engine is arguably not yet ready for large scale, reliable commercial use, vapour absorption chilling is a mature technology today, and organic rankine cycle is already a commercially available solution.
VAM (vapour absorption) route will be especially useful for factories having significant cooling requirements, either in terms of air conditioning or for chilling/refrigeration.
CHP/cogen is already quite prevalent in the sugar mills and distilleries in India. For those facilities that have large amounts of waste heat, CHP is a viable and financially rewarding option.
Concentrating Solar Thermal
Until a few years back concentrating solar heat was used predominantly for power generation – known as concentrating solar power (CSP).
But today, using the same CSP technology as the base but with lesser sophistication, solutions are available that allow concentrating solar heat to generate steam up to 200OC, something that can be used in many process industries for most of their heating purposes. This has opened up the new domain of concentrating solar thermal (CST).
CST is today a commercial solution and has already been adopted / implemented at many process industries in the country including diaries, food manufacturing units, large canteens and kitchens and the like.
In most case, CST might not be able to replace conventional fuel use fully. It has however been estimated that it could replace up to 75% for many installations. That can be a tremendous saving for companies that are bearing the brunt of fast increasing furnace oil / LPG / diesel prices.
Unlike solar water heaters, which is a highly mature technology, CST is still undergoing significant innovations, thus making it possible for companies to have high efficiency and high productivity technology installations in the near future.
CST has been shown to have payback periods of less than 3 years in the installations that it is already operating in India.
Energy Efficient Heating Equipment
I recall a trip I made to a well-known hotel in Chennai where the chief engineer said said that by just replacing one old pump with a new, efficient one, they were able to reduce about 5% overall in electricity costs. This moral is true for many heating appliances and equipment too – be they boilers, furnaces, ovens or kilns.
Of course, the decision is usually harder as the capital costs involved in changing over could be considerable, as these heating equipments will usually form the bulk of the cost of the overall heating system.
Back-pressure Steam Turbine
Back pressure steam turbines are not exactly for thermal efficiency or for reducing your heating costs, but I thought I’d include these here as they still provide a better bang for the buck from the heat generated.
Back-pressure steam turbines essentially use the extra pressure and temperature that are inevitably present in the process steam to drive a small non-condensing turbine to generate power. The steam that leaves this back-pressure steam turbine goes on to do the useful work.
As mentioned earlier, while it does not provide heat at a lower cost, it provides more value for the same amount of energy used for heating, by generating additional power from it.
There, you have it.
Using one more of the above six avenues, factories that use significant amounts of heat can achieve significant cost savings while at the same time becoming far more “green” and environment friendly.
Wish to know more on how your factory could be made more green through sustainable heating solutions? Send a note to me – Narasimhan Santhanam ( firstname.lastname@example.org ).
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