I’m always looking for ways to slash at my utility bills, and evidently, I’ve been handed a shiny new scalpel. Hydropower is making waves, but while we’re familiar with hydro dams, it’s not immediately clear how hydro can be applied at home.
Hydropower for homes is a form of small-scale solar power that harnesses the kinetic energy of adjacent waterways, converting it into electricity for home use. The systems rely on steam-driven turbines, generating energy that can be stored in batteries for later use.
This article will look at:
- What hydropower for home involves.
- How hydropower for home works.
- The architecture of hydropower for home.
- Various types of components employed.
A few discrete steps are required to assess whether hydro is a solution that can save you money and keep the lights on. We’ll look at what needs to be considered, what the options are, and how to move from assessment to a practical configuration.
What Is Hydropower For Home?
Hydropower for homes is a system of electrifying homes by tapping into the latent energy of nearby water sources. A kit is attached to amplify the force of the moving water (if necessary), generate energy from the moving water, and reconnect the water to its source.
In spite of the technical difference between “energy” and “power,” the terms “hydroenergy” and “hydropower” are used interchangeably to refer to what is defined here.
At the bottom of this process is the water cycle, a seven-step process involving:
- Evaporation: Heat from the sun turns moisture in bodies of water (the hydrosphere) into vapors. These light water particles travel through the air into the atmosphere.
- Condensation: Cool temperatures high in the atmosphere cause the vaporized particles to form ice particles and droplets. These coalesce to form clouds.
- Sublimation: Parallel to evaporation, sublimation involves the direct vaporization of ice into vapor. This process is direct in that it does not require an intermediating conversion of ice to liquid. Polar ice caps and snowy mountaintops are the primary sources of sublimation.
- Precipitation: Water hits the surface of the earth when the vaporized droplets condense to mass levels at which they can no longer be sustained in the air. Wind and temperature changes catalyze the process.
- Transpiration: Some of the precipitate soaks into the earth and is absorbed by plants. The process in which they become part of the body mass is known as transpiration.
- Runoff: The bulk of the water that does not transpire runs over the surface of the earth under the influence of gravity. It forms streams and rivers that terminate in lakes, seas, and oceans.
- Infiltration: This happens parallel to transpiration and runoff. It involves water that sinks into the soil without being absorbed by plants or evaporation. This precipitate lodges into the earth’s water table.
Hydropower converts the kinetic energy in the runoff phase. Because the cycle is kicked off at step1 by the sun, hydro energy is considered a form of solar energy.
How Does Home Hydropower Work?
Home hydropower uses miniaturized versions of large-scale hydropower. The underlying principles are the same. Home hydro systems will, in their overall design, look familiar to anyone who has seen the structural layout of a hydro dam.
Types Of Hydropower Systems
Hydropower systems can be classified in two ways: by output and architecture.
Hydropower By Output
When hydropower systems are differentiated by their maximum output, the following categories are recognized:
|Single / Cluster
While most houses get some of their electricity through grid-fed hydro (in Norway, this figure is 98% of supply), hydropower for homes relates to the bottom three types in our table: micro, pico, and family.
Hydropower By Architecture
Hydropower systems come in the following types of configuration:
- Storage (Reservoir): Reservoir systems dam water for use when the main source (usually a river) yields little flow.
- In-Stream: Here, a run-of-river system is immersed in the stream, obviating the need for diversion.
- Pumped Storage: This is a net consumer of energy but forms a basis of storage and regulation of energy. It is the largest form of grid energy storage capacity worldwide.
- Run-of-River: These use the flow of a river or stream with little or no storage. Water is diverted to the pump and redirected to the source stream.
- Ocean Energy: This is an emerging technology, tapping the kinetic energy inherent in tides. Wave and tidal converters are being developed for micro hydro applications.
Home hydropower system uses run-of-river architecture. Pumped storage is used in hybrid situations where lakes and collateral energy sources are available. For coastal dwellers, ocean energy is a promising new technology under development.
Architecture Of Home Hydropower
Home hydropower systems typically are stream-driven. They consist of the following components:
- Water Source: This stream is usually naturally occurring but could be synthesized by streaming water off a distance source.
- Water Conveyance: This channels the water to the transformer. Penstocks are valve-controlled conduits that pressure the water for increased energy (see “flow” below).
- Rotational Transformer: This is a waterwheel, pump, or turbine that transforms the kinetic energy of the moving water into rotational energy. These devices are shaped so that the effect of the water moving over them effects the transformation.
- Alternator/Generator: This component transforms the rotational energy into alternating current, the sought-after electricity.
- Regulator: This component controls the action of the alternator.
- Wiring: This electrical conduit delivers the electricity to the home.
Turbines are customized for variances in pressure and volume of the incoming water. The following types are available:
These turbines assume that the incoming water will drop from a great enough distance to generate high terminal velocity. They have the simplest design. The following variations are available:
- Pelton Wheels: These assume low volume and high incoming velocity. They use principles of jet propulsion to drive the turbines. The incoming water is driven through a pressurized conduit ending in a sprayer.
This nozzle directs water into two curved buckets that propel the wheels. They have high-efficiency rates in the 70-90% range – indicating the amount of energy that is not lost to friction and leakage in the kinetic-rotational conversion.
- Turgo Impulse Wheel: This is an improvement on the Pelton. It is smaller and uses three angled buckets rather than two. It moves faster, requires less supporting infrastructure in the form of gears, and performs more robustly.
- Jack Rabbit Turbine: Unlike the Pelton and Turgo, the Jack Rabbit is designed on the assumption of no vertical drop. It can be placed in a horizontal stream generating up to 2.5kWh per day in ideal conditions.
These are turbines that rely on the pressure rather than the velocity of incoming water. While the blades of an impulse turbine take turns making contact with the water, all reaction blades are constantly in contact with the water.
While these turbines are favored for large projects, their high cost and complex construction usually put them out of contention for micro-hydro. An exception to the aforesaid rule is the propeller turbine.
Propeller turbines work much like a boat’s propeller. Three to six angularly aligned blades attach to the runner. This design is highly efficient. The Kaplan turbine is a variant of this design that is suitable for micro-hydro.
Pumps And Waterwheels
These are the remaining two types of rotational transformers.
Pumps act like turbines when their action is reversed. They are favored in micro-hydro for two reasons:
- Mass production means that they are readily available, cheaper to procure, and easier to replace than dedicated hydroelectric turbines.
- Pumped hydro (see below) requires a transformer that can switch between pumping and transforming. By switching between normal and reverse behavior, pumps comply with this request.
The downside to pumps breaks down like this:
- They require constant water pressure and volume.
- They’re less efficient than pumps.
- Compared to pumps, they are less robust.
Waterwheels have fallen out of favor due to their unwieldy design and slow operation. They were the first transformers in use, having powered mills for centuries.
Micro Pumped Hydropower
Static sources like lakes do not support run-of-river hydropower. Micro-pumped hydropower works in cases where:
- An adjacent lake or large pond is situated above or below a steep incline.
- The homeowner has a complementary energy source, like solar panels.
Assume for illustration that the lake sits at the bottom of the incline. The user fits a pump to drive water from the lake to a reservoir at the top of the incline. By day, the solar system powers the pump feeding the reservoir.
By night, the directionality of the pump is reversed, and it acts as a turbine. A sluice is released on the reservoir, streaming water to the turbine. This turbine converts the kinetic energy of the dropped water to hydro energy.
This is a way of storing excess solar energy harvested during the day, creating a round-the-clock supply. In the case where the lake is atop the incline, the lake acts as the reservoir, and it is replenished by day from an actual reservoir on low ground.
Microhydro and some pico hydro applications have the potential to cater to a number of homes. For pico hydro, the distribution to the recipient household could be done from the wiring of the installation. For micro-hydro, it may be convenient to connect to the grid and lever off its distribution.
When connecting to the grid, the local utility should be contacted for authorization and guidance. The steps to grid connection run roughly as follows:
- Electricity flows to the grid through a connection mechanism. There are two options:
- Fixed-Speed Induction Generator: Induction generators are energized by the grid and are the most common way of connecting. A consequence is that the hydro system shuts down during a power cut.
- Grid-Tied Inverter: The inverter sits between the generator and grid, which powers it. This allows the hydro system to function in the event of an outage.
- On the opening of the water inlet, the turbine starts to rotate.
- With increased throughput of water, the generator produces current but at a lower frequency and voltage than the grid accepts.
- The control system adjusts the flow rate, setting the power to the grid’s required level.
- The electricity waveforms of the generator and grid are synchronized by the controller.
- On synchronization, a contactor is automatically closed to connect the grid via the generator or inverter.
What Are The Hydropower For Home Pros And Cons?
The balance of advantages to home hydro energy would differ between users, largely tracking geographical variances. Some factors are common. We list the factors that should be weighed in assessing the technology:
- Renewable: Because of the water cycle, home hydropower is a renewable resource. There are global concerns around water scarcity, but these are orthogonal as hydropower does nothing to consume water.
- Clean: The process has no noxious emissions at all. No carbon derivatives are released into the environment, and nothing is done to contaminate the water sources.
- Simple: The technology is simple, which reduces the reliance on skilled installers and maintenance personnel. Faults are easier to troubleshoot by lay users.
- Reliable: Hydropower has a long history through which it has demonstrated its low error rate.
- Safe: By the scale of electrical installations, there are low-impact risks associated with failure.
- Developmental Impact: Microhydro has been successfully deployed amongst marginalized communities. The cheap power that this provides has delivered developmental impacts in terms of improved quality of life.
- Limited Streams: Home hydro requires moving streams that are not in abundant supply. This changes with the emergence of ocean energy, but even that has coastal limits.
- Rural Bias: Further to the point above, the technology tends to have a rural bias. The streams in urban spaces are less likely to be accessible, and urban population density limits the breadth of their impact.
- Topologically Sensitive: Even where streams are available, they need to be steep and heavy for the right amount of power to be generated.
- Drought Prone: Where streams are seasonal, hydropower evaporates in the dry months.
- Intrusiveness: The technology can have an intrusive impact that might interfere with marine life or the aesthetics of the brook.
How Is A Home Hydropower System Planned?
A few discreet steps stand between theory and the implementation of a hydro system for your howe. Conduct some research to confirm that there is no local installation that you can feed off. In the absence of that, do the following.
Assess Your Energy Requirement
There are two ways:
- Pro Forma: Use this method if you have no history on the site you intend to occupy. Consider the power requirements of all the domestic applications you intend to use. Multiply their energy requirements by the time you intend to use them and sum the answers.
- Historic: If you have lived in the home, simply consult your historical utility bills where actual usage is recorded.
The significance of this step is that you have to match the energy potential of your installation with your domestic energy requirement. Failure to meet those ends should preclude the installation.
Measure The Energy Potential
The next step is to measure the potential energy that can be obtained from your site. The three main determinants are:
- Head: This denotes the vertical distance between the source of water and the inlet. The greater the head, the more kinetic energy is available, has gravity works over a longer range. The unit is meters, where 1m = 1.0936yd.
- Flow: This denotes the amount of water that flows past a point per second. More flow implies more mass, which implies more kinetic force. The unit is liters per second, where 1l = 0.26417gal.
- Efficiency: Efficiency is a percentage – usually between 50-95% – that indicates the energy-retention rate of the turbine.
The site’s energy potential is given by:
Power(W) = Head x Flow x g x eff, where
- g is the gravitational force, = 9.8
- eff = turbine efficiency. This is a function of the installed equipment.
Power [W] = Net head [m] x Flow [ l/s] x 9.81 [m/s²] (est. gravity constant) x 0.5 (turbine/generator efficiency)
When accessing a water source like a river, permission from the local authority would be required. Before spending on anything, get a sense of whether it is possible to obtain permission and what is required for a successful application.
Even when planning a full DIY system, it is worth soliciting help in key areas. Some of the areas to consider are:
- Feasibility: Consulting engineers may help with assessing the feasibility of your installation. Apart from doing their own study, they might be able to offer an opinion on your own assessment.
- Installation: Profession installers would be able to help with technically difficult parts or the whole of your installation.
- Procurement: Contractors may give informed views of the best locally available components.
- User Experience: Chatting to other home users will give a sense of issues to avoid and features to look out for.