Here is a detailed post about Hydrogen Energy Storage Efficiency. Suppose you are looking for hydrogen energy storage pros and cons. Then reading this article may help. It also includes hydrogen energy storage companies.
All six steps in the chain of process steps involved in hydrogen energy storage system as shown in Figure 10.2 are associated with losses. Power conditioning is required at the beginning of the chain when grid power and the power demand of the electrolyzer need to be matched as well as at the end when floating voltage DC from the fuel cell needs to be converted into either AC or fixed voltage DC.
hydrogen energy storage pros and cons
Hydrogen Energy Storage Efficiency
The efficiency of water electrolysis is dependent on the technology used, the hydrogen production rate and the pressure level . In this study, typical figures for alkaline electrolyzers are in the range of 5.5–4.5 kWh∗Nm−3 for pressurized operation and 4.6–4.3 kWh∗Nm−3 for atmospheric operation. A decrease in specific energy demand with increasing production rate has been observed. Energy consumption of PEM electrolyzer systems were between 6.5 and 4.5 kWh Nm3 h−1 also with decreasing energy demand with increasing hydrogen production rate. The PEM electrolyzers analyzed in this study covered a smaller band of hydrogen production rates. When the practical energy demand as shown in  is compared to 3.54 kWh Nm−3 theoretical energy demand of water electrolysis from the liquid phase, the efficiency of hydrogen generation is in the range of 64–82% depending on the size of the electrolyzer.
Hydrogen conditioning for storage requires the removal of residual oxygen, hydrogen drying, and compression to the final storage pressure level. There is little technical information available on the efficiency of the individual steps of hydrogen conditioning. The compression of hydrogen to the chosen storage pressure is one of the major factors. Approximately 10% of the energy content related to the lower heating value (LHV) must be taken into account for a storage pressure of 200 bar, while storage at 800 bar requires about 15.5%. Liquid hydrogen storage uses up to 40%. Metal hydride storage is more energy efficient using only 5–8% of the LHV of the stored gas . It has to be noted that pressurized electrolyzers can directly fill medium pressure hydrogen tanks at a pressure level of approximately 40 bar with minimum extra electrical energy demand as compared to pressure less electrolysis. Losses from oxygen removal and hydrogen drying are difficult to assess. An experimental study using a 1.5 kW electrolyzer in a simulated solar cycle has been carried out . A total of 4.29 Nm−3 of hydrogen has been produced using 22.3 kWh (5.2 kWh × Nm−3) in a given study campaign from which 4.25 Nm−3 have been stored in a metal hydride. From the balance of plant, 2.1 kWh has been consumed by the controller while 1.7 kWh has been used in the purification unit (catalytic oxygen remover combined with a molecular sieve dryer).
The conversion of hydrogen back into electricity can be classically done by using internal combustion engines (ICE), gas turbines, or in the very large scale combined cycle power plants. Efficiencies range from approximately 30% for gas turbines and up to 60% for large scale combined cycle plants. Engines and gas turbines compatible with hydrogen are still in the development phase. In general, gas turbines designed for operation on natural gas can be operated on hydrogen. However, in order to keep NOx-emissions in check, the flame temperature must be kept at a low enough value. This can be done by diluting the hydrogen fuel with inert gasses such as nitrogen or steam .
A different option for electricity generation is fuel cells. As mentioned before, fuel cells are generating electric energy by directly providing electrons via two coupled but spatially separated electrochemical reactions, namely the hydrogen oxidation and the oxygen reduction. The efficiency of the fuel cell is primary related to the kinetics of the electrochemical reactions involved and the internal resistances encountered in the cell. Both kinetics and internal resistances are lowering the cell voltage resulting from the potential difference between oxygen reduction and hydrogen oxidation which theoretically is 1.23 V at 25 °C and under atmospheric conditions when water is generated in the liquid phase. It is evident from the current–voltage curve shown in Figure 10.5 that this theoretical value is not even reached at open circuit voltage.
The efficiency of a fuel cell can be defined by the amount of the electric energy generated divided by the enthalpy of combustion of hydrogen. One has to differentiate between the so called higher heating value (HHV), in which case water is formed in the liquid phase and the LHV where water is remaining in the vapor phase.
By expressing LHV and HHV by their voltage equivalents (1.24 and 1.47 V, respectively), one can easily calculate the efficiency of the fuel cell. The difference between electric energy recovered and combustion enthalpy (heating value) can in principle be recovered as heat.
Additional losses which are taking place during operation of a fuel cell such as parasitic energy demand for balance of plant components etc. cannot be assessed so easily.
Fuel cell systems are well suited for use in combined heat and power applications. Several demonstration projects have been set up mainly using polymer electrolyte membrane as well as phosphoric acid fuel cell technology. These demonstrations have been in the power range from a few kW to the MW range. The efficiencies of low temperature fuel cells operated on neat hydrogen can be above 50% depending on the operating point and the balance of plant layout.
When operated in CHP applications in residential buildings, the thermal energy provided by the fuel cell typically is too small to cover the whole heat demand of the building. However, the heat released from the fuel cell system per day is matching the heat demand for hot water production pretty well. Any additional heat demand in the building must be provided by a separate boiler installed in parallel to the fuel cell system.
When low temperature PEMFC are used, only heat at a temperature up to 60 or 70 °C can be recovered. While this temperature is sufficient to provide input to low temperature floor heating systems or for the preparation of domestic hot water, more valuable heat to be fed into industrial processes cannot be gained from low temperature PEMFC.
Although the theoretical efficiency of electrochemical hydrogen conversion is decreasing with increasing temperature, high temperature fuel cells such as SOFC or MCFC might achieve even higher efficiencies, since due to the higher temperature, kinetic losses related to oxygen reduction are significantly reduced. However, as mentioned above the heat management concept of SOFC and MCFC systems is normally involving heat removal by internal methane reforming which is missing once these systems are operated on neat hydrogen. Furthermore, MCFC systems need a steady supply of CO2 enabling the charge transport in the electrolyte which would need to be fed from outside. Therefore, a different system layout would be necessary requiring additional components in the balance of plant and adding to cost and complexity of the total system.
The overall energy efficiency of electricity generation can be improved by using the heat generated in the process. In combustion engines or gas turbines this is done by using an organic rancine cycle process to convert the energy of the hot exhaust gasses to electricity. The low temperature heat from the engine can be fed to district heating systems increasing the overall energy efficiency. The waste heat from large scale combined cycle plants is normally at a temperature level which cannot be used further.
In the case of fuel cells, heat is used in small-scale combined heat and power plants normally operated on natural gas. PEMFC, PAFC, and SOFC systems have been developed and are currently in the phase of market introduction. The use of high temperature fuel cells could also provide more valuable high temperature heat for industrial processes. This has been demonstrated in different MCFC applications where the high temperature waste heat has been used as process heat for rubber processing, to sterilize equipment in hospitals or to provide process heat for breweries or food processing plants. Due to their increased operating temperature, high temperature PEMFC are also an attractive option for combined heat and power generation. In this case, the temperature of the heat recovered is high enough to supply more demanding applications such as the sterilization of medical equipment of the provision of low temperature steam for industrial building management.
hydrogen energy storage companies
Some Benefits Of Hydrogen Powered Cars
Cars with hydrogen fuel cells instead of the typical lithium-ion batteries from electric cars offer an attractive value proposition that seems to get rid of the problem of the end of the lithium batteries life cycle. This is a plus as for now, at a time when there’s still some uncertainty about the future of these batteries (from cars, but also from solar panels, cellphones and others) once they no longer serve their main purpose. They’re hard to recycle and some projects are being developed to reuse them as back up generators in urban buildings like hospitals.
As well, driving without any polluting emissions (as would happen if we considering renewable energy grids are growing worldwide with decarbonization) with the plus of being quickly refueled in 5-10 min compared to the best case scenario of 40 minutes charging or the most common scenario of 3-6 hours charging in electric cars, is an unquestionable win for the hydrogen mobility movement too.
Some studies also show the hydrogen economy has the potential to decrease global CO2eq emissions between 0 and 27%. This potential can be met once 1) methane leakages from natural gas are relatively low, 2) methane cracking is employed to produce hydrogen, and 3) a hydrogen fuel cell is applied.
Electric Cars Vs Hydrogen Cars – Which Is More Sustainable?
Despite the benefits mentioned above, most hydrogen today (95% the US) is produced by the process of methane reforming. This tears apart all the potential of hydrogen-powered vehicles as a solution to fight climate change because of the carbon monoxide and dioxide that are generated in the process. As well, the need to use natural gas (a fossil fuel) that might escape during the extraction and transportation (via pipelines) phase isn’t very convincing either. Even if the methane cracking process is improved (and efforts aren’t turning that way) it isn’t likely to be a long term solution.
Yet, as technology develops, perhaps the water electrolysis process of getting hydrogen can be improved and further used as the process gets more efficient. Because the fact that hydrogen cars mean using energy twice (to make hydrogen and then using it to power vehicles) while electric cars can use the energy from the grid straight away is a strong argument in favor of electric cars. All because after converting electricity into hydrogen and back to electricity might involve energy loses up to 45% (including compressing it into a liquid and storing it), making it a not very efficient process.
However, while new methods of producing hydrogen are being developed, such as the proton exchange membrane, which, according to scientists, might get to an 86% efficiency, we need to wait and see what happens. Using the extra energy supply for hydrogen production and creating some hybrid version of hydrogen-lithium-ion cars can also be something, once more studies come out clarifying whether this surplus energy is more efficient to use in dams (not considering their other impacts) or producing hydrogen. As for today, electric cars are a more accessible vehicle – regarding the different types of cars and charging points. They include more efficient processes compared to hydrogen-powered cars and if their lithium batteries are re-used to meet different ends they’re liking to stay a more sustainable solution, at least over the next few years.
Used Car Websites
Buying a new or used vehicle is a big decision — both financially and in terms of the amount of time we spend in our cars. And wouldn’t you know it, there’s an app for that. Cars, trucks, and SUVs of all types can be found online today. You don’t even need to leave your couch to research, browse, inquire, and finance your next vehicle.
Here are some of the best used-car websites around.
Because it’s an aggregator (like Kayak.com), the easy-to-use Autolist site displays millions of vehicles from many different sources. Users can view details such as the length of time a given vehicle has been on the market, plus any price changes for that vehicle. Autolist has one of the highest-rated used-car apps available. It works with Android or iOS phones, and just like the website, it checks multiple online databases to help you locate your dream car. The app also has instant price-drop alerts and high-res pictures to help you find the best deals on the most local listings. Shoppers can even apply for financing. With family sharing, as many as six family members can share information through the app. Add to that reviews, industry insights, a Rotten Tomatoes-style aggregator of older vehicle reviews, and buyer’s guides to help steer you through the car-buying process.
Like some of the other websites here, AutoTempest’s search results are drawn from multiple sources. Their website and app work similarly to the others, including the ability to save searches. They have lots of other useful information as well, including an up-to-date blog, buying guides, and car reviews. While you can filter your searches, the criteria for doing so are much more limited, although some might consider it to be streamlined. Either way, the essential information is provided. Choices include make, model, distance, price, year, mileage, vehicle type, transmission, and whether it’s for sale from a private party or by a
Because Autotrader.com nearly predates the internet itself, its longstanding reputation has built up decades of trust. Available as a website since 1997, it has over 3 million listings drawn from 40,000 dealers and 250,000 private sellers, and its selection is immense. The website has a wide variety of filters that can help you narrow your search down to exactly the type of vehicle you’re looking for. You can save your searches and even apply for insurance and a loan.
Bring A Trailer used to be a listing of interesting cars for sale around the country, now it is a full-blown auction site, with rare and unusual vehicles selling for sometimes astounding figures. It is the place to find that social ride or merely kill endless amounts of time browsing high-dollar exotics and absurdly clean early 2000s commuters. Recently, a pristine 2000 Honda Civic SI sold for $50,000. If you are in the market for something unusual or are willing to pay top dollar for your dream car, check out BaT.
This is a company that seeks to build trust through transparency. You will find many of the same search options on their website as you’ll find on the other sites. However, you’ll also find the CarGurus valuation of a given vehicle based on typical search criteria on top of this. This algorithm is similar to the methods used by KBB. The information they use to make this determination includes comparable car listings and pricing data on vehicles that have recently sold. Ratings are based on mileage, trim, vehicle history, and a multitude of other factors. CarGurus rates each available car deal as being Overpriced, High, Fair, Good, or Great.
Carmax is a dealership specializing in high quality used cars, many available with the internet-famous Carmax warranty. This website isn’t the best for those looking for a killer deal because of their no-haggle policy, but it is an excellent place for people who want the most effortless car shopping and buying experience. For those looking for the ease of browsing and buying online, without the anxiety-inducing Craigslist test drive, Carmax can be a good option. Browse, buy, and the car can be ready for pick up, virtually all online or on their mobile app.
Cars.com is one of the largest automotive search engines. With thousands of listings covering almost every car, there is also a new tool that rates the value of used vehicles relative to the current market trends. Cars.com has fewer private sellers, but it’s a great way to search dealers in your area and compare pricing for similar vehicles. It also has extensive sorting options to narrow your search by the specs and features you are looking for and leaving out those you don’t want. In addition to consumer reviews, the site has now built up an extensive archive of expert reviews written by its editorial staff.
This site works to simplify buying a car, and like Autotrader and others on this list, they can help find financing. The search criteria include make, model, distance, price, mileage, year, color, engine, and even photo availability. CarsDirect also has buying guides, rankings, and vehicle comparisons. Like similar sites, you can save your searches and vehicles of interest. The website also has educational videos, including reviews, car news and reports, and tools that include a trade-in valuation.
Carvana is another used car dealer that built a business around making the buying experience easier. Buy with confidence with a 7-day money-back guarantee, and have the car delivered to your door. All Carvana vehicles have accident free vehicle history and pass a 150-point inspection. You can also sell your vehicle to Carvana, even without buying from them. They claim you will get a real offer after filling out a form, which takes just a couple of minutes. With used car values near all-time highs, it may be a good time to see what your car is worth to them. Carvana is also the inventor of the car vending machine for those looking to buy in person. It’s a neat gimmick worth checking out.
Primarily a classified site, Craigslist doesn’t have many fancy graphics or options, but the site’s selection is fairly broad, and postings usually include photos. You’ll need to be super savvy if you’re going this route because the site is rife with scammers, but it is possible to negotiate a worthwhile deal here. Search filters here include distance, price, make and model, year, mileage, condition, number of cylinders, drivetrain and fuel type, color, size, title status, vehicle type, and transmission type. A point of interest to some, some sellers on Craigslist might accept cryptocurrency like Bitcoin in exchange for the vehicle they’re selling. You can also create email alerts for the specific attributes of a vehicle that you’re looking for.
eBay Motors isn’t just an auction site for rare vehicles anymore. There are thousands of used and new cars listed by dealerships and private sellers to peruse using classified-style listings. Whether you are shopping for a custom show car or a late model Chevy, eBay likely has at least one of those vehicles. Other great searches on eBay motors include the “Replica/Kit Make” section, as well as the “Racecar (Not Street Legal)” category. Just be careful in terms of trusting sellers since eBay makes it difficult to recoup any monies lost to fraud or misrepresented vehicles. A pre-purchase inspection by an independent third party is highly recommended if you’re not able to see the vehicle yourself in person before buying.
Edmunds originated as a paperback booklet available at newsstands. Decades of experience have made this a well-respected name in the industry. The website allows you to save searches and favorites and also lets you filter your selections. Although their search functions look similar to the ones available on other sites, they often have more features and options to choose between. That allows buyers to narrow and refine more thoroughly. Edmunds also has a wealth of advice and articles to help educate people about the car-buying process and the vehicles themselves.
If you don’t mind a car with plenty of miles on it, Enterprise’s former rentals can be a good choice. They offer a no-questions-asked, seven-day “buyer’s remorse” period, in addition to their 12-month or 12,000-mile limited powertrain warranty and one year of roadside assistance. Enterprise also provides financing. Unlike most of the other sites mentioned here, the company sells cars only from one source: their retired rental fleets. They also take trade-ins and have special programs for college graduates or first-time car buyers. The website allows you to search by the monthly payment you can afford alongside the same criteria you’ll find on other sites.
For classic car, truck, or motorcycle collectors, this is a ‘don’t-miss’ destination. As well as vehicles, Hemmings helps you locate hard-to-find parts for project cars. Search for vehicles or parts by make, model, type, price range, and category. With more of a community feel to it, this site maintains a blog and regularly sends out newsletters. Hemmings also sells merchandise related to this niche market. They have an email list, fantastic videos, and special events, not to mention apps for Android and iOS, and several print publications to subscribe to.
The words “Blue Book price” have been a part of the American vocabulary for nearly a century, and the Kelley Blue Book website and app both trade on this longstanding name recognition. Not only are they known for providing accurate estimates of your car’s market value, but their site has tools for checking your credit score and calculating car payments too. Expert reviews, top ten lists, and recall postings make this site a longtime go-to favorite for automotive information. They also cover motorcycles, snowmobiles, and personal watercraft such as jet skis. KBB even has an instant cash offer section on their website.