Co-gen, Tri-gen, Solar, Micro wind: Which options stacks up best?

Many technology options have been developed to enable a transition to a more sustainable energy future. Some options, such as solar power, are more familiar than other proposed alternatives, like tri-generation (also called Combined Cooling Heat and Power – CCHP). This article will look at four types of renewable energy systems and their associated reliability and costs to show how they compare to one another. The four specific systems include Cogeneration or Combined Heat and Power (CHP), Tri-Generation (CCHP), Solar, and Micro-Wind.

Tri- and Co-generation both utilize the concept of increasing efficiency through colocation of services. Traditional electricity production through the combustion of a fuel source successfully creates useful electricity, but also creates an enormous amount of heat that is dissipated as wasted energy. To get an idea of how much energy is wasted we only need to look at coal and natural gas plants as an example. The burning of coal for electricity is a process with maximum efficiencies around 30-35%. That means that over 65% of all the energy in coal use is lost through wasted heat. Natural Gas plants are more efficient that coal, but still waste over 45% of the energy to heat loss.

Cogeneration solves much of this issue by combining heat pumps with traditional power engines in an attempt to capture much of the heat that is often wasted. The result is a combined system that uses fuel two times more efficient than regular power generation. The input fuel is still combusted for electricity, but the heat pumps are connected in line to collect the heat and either create more electricity or distribute the heat to be utilized in hot water lines or air conditioning. While this process is highly efficient, the addition of heat pumps, wiring, and system integration increases system complexity adding significantly to capital costs.

Tri-generation builds on the concept of cogeneration by integrating cooling systems with cogeneration system to supply local cooling, heating, and electricity. As expected, adding the cooling system further increases efficiencies by utilizing more system outputs for useful ends, but this is accompanied by a further increase in costs.

Solar power may be the most talked about renewable energy technology in the world. Solar power has been developed for decades and has experience drastic price reductions over the past 20 years. By capturing photons from sunlight to create electricity, solar panels utilize the world’s most abundant resource to create the world’s most useful form of energy, electricity. While lab-scale technology has reached higher efficiencies, commercially available solar panels are typically around 20% efficient. This doesn’t sound like much, but when you consider that solar panels have no moving parts and are simply capturing available light for electricity production, efficiencies do not hold much sway. The inefficiencies only account for the mathematics of the chemical reactions, and the fact that solar power requires no fuel source is even more impressive. The cost of most solar panels result in a payback time of around 5-10 years, although most countries have subsidies in place that reduce this to less than 5 years.

Wind energy, like solar power, requires no fuel input; simply place the wind turbines and wait for the wind to blow and create electricity. Wind power is less mature than solar and has significantly more placement issues due to size, scale, and geography, but has experienced regular price reduction in the past 10 years. Overall costs tend to be similar to solar, and since wind power creates electricity from kinetic energy, the most efficient transition, wind power can reach efficiencies up to 50%.

When choosing among options, cost is key, but it is not the only determinant. Wind power is efficient and many times cost effective, although placement is regularly an issue. For example, urban households have an extremely low probability of ever utilizing wind power due to difficulties in installation and permitting. On the other hand, solar power is the most modular of any renewable energy source, and since the sun shines everywhere (albeit with varying intensity) households in any location have the ability to install solar right onto their roof. Tri-generation and Cogeneration are typically too expensive for any one consumer to afford and make more sense from an installation perspective at a larger scale. For example, industrial building could pay to install these systems and utilize the high efficiency to save fuel and money by combining heat and power at large scale.

Of all the systems we described solar power is by far the most popular. Adoption all over the world has been increasing at an exponential rate. This growth is also aided by cost reductions due to learning and economies of scale, and often from government incentives. Solar power takes advantage of lower cost and simple technology and installation to outperform tri- and co-generation, while improving modularity and applicability to beat out wind power. As far as decreasing carbon emissions and moving toward a sustainable energy system, consumers can’t go wrong, but the solar power recipe seems to be just right.

  • 27 Mar, 2014
  • Kit Man Chan

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